source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-3644 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
Eukaryotic cell division involves mitosis and what? | [
"spermatogenesis",
"meiosis",
"electrolysis",
"cytokinesis"
] | D | Eukaryotic cell division involves mitosis and cytokinesis. |
SciQ | SciQ-3645 | concentration
Title: Why would sodium ions want to go down just because of one side is more positive than the other? From Khan Academy starting from 1:25, the narrator, while talking about the Electrochemical gradients, said that sodium ions would naturally want to diffuse
down when having a high concentration up here and a low concentration down there.
My question is Why would sodium ions want to go down just because of one side is more positive than the other, I mean, isn't the same charges repelling each other? I don't think the degree of positivity will enable them to be attracted to each other.
Could anyone help me explain this? This has more to do with the diffusion gradient. Sodium ions move from the region of their higher concentration to a region of their lower concentration.
In the example given by you, I believe, there are additional negatively charged molecules present in the inner side of the membrane, resulting in an influx of sodium ions to balance the same. However, like charges do repel, so this influx is not indefinite, but only up to a certain extent- until the electrical potential difference across the membrane exactly balances the concentration gradient. This point is known as the equilibrium potential.
(This question and answer might be more appropriate in the Biology SE, I think).
The following is multiple choice question (with options) to answer.
Why do sodium and chloride ions attract each other? | [
"like attracts like",
"magnetism",
"sulfides attract",
"opposites attract"
] | D | Sodium and chloride ions have equal but opposite charges. Opposites attract, so sodium and chloride ions attract each other. They cling together in a strong ionic bond. You can see this in row 2 of Figure above . Brackets separate the ions in the diagram to show that the ions in the compound do not share electrons. You can see animations of sodium chloride forming at these URLs:. |
SciQ | SciQ-3646 | resources, soil
Title: Is soil a renewable resource? My geology textbook tells me that soil is not renewable, and I agree with this, but there was some question in my class as to whether this is true.
Some soils take more than a human lifetime to regenerate. However, in crop production, it seems as if soil can be regenerated with additives.
In the scientific community of soil scientists, is soil considered a renewable resource by most of those scientists? Is there strong evidence to support this? Soil is an interesting case because although it is non-renewable (at any useful rate) as a 'bulk material' once removed from the ground, the nutrient content of soil can be renewed with fertilizers.
What a soil-scientist would understand as 'soil' is ultimately produced from the physical and chemical breakdown of solid bedrock at the base of the soil horizon. The rate at which this happens for natural soil production can vary substantially depending on the climatic conditions and other factors, but typically could range from 0.1 to 2.0 mm/yr.
In many intensively farmed regions, (top)soil is being removed by erosion much faster than it is being replaced by natural process. Removal of vegetation cover is enough to expose bare soil to rainsplash erosion at rates much greater than it is renewed. Once soil is bare, it becomes much more susceptible to erosion.
I think the additives you are referring to replenish the nutrient content of the soil, and not the the bulk material that would be produced by bedrock decomposition. With careful management, the fertility of existing soil can be maintained. But if the soil is allowed to be washed off or erode, for all practical purposes, the rate of replenishment is not fast enough for it to be classed as renewable in that sense.
This site has links to more aspects surrounding this issue.
The following is multiple choice question (with options) to answer.
What layer of soil, essential for farming, has the highest proportion of organic material? | [
"topsoil",
"bedrock",
"humus",
"subsoil"
] | A | Topsoil has the highest proportion of organic material. Topsoil is essential for farming. |
SciQ | SciQ-3647 | genetics, homework
Title: "structural and regulatory elements of genes" Can anyone please explain a little about these two elements of genes? My main problem is with "which ‘switch on’ instructions".
genes have structural elements (which code for a particular protein) and regulatory elements (which ‘switch on’ instructions) The expression of protein coding genes happens by the process of transcription. So promoters facilitate access of the RNA polymerase complex to DNA to begin transcribing a locus on the genome. The promoter of a gene often contains sequences that bind proteins called transcription factors, which play a role in various parts of the transcriptional process as well as components of RNA polymerase themselves (Such as a Pribnow box in prokaryotes, or a TATA box or an initiator element in animals).
So whether a gene is turned on and if so, how much it is turned on, is a property of how many transcription factor binding sites exist in the promoter, the nature of the transcription factors themselves in terms of their influence on transcription, and in eukaryotes and some archaea, epigenetic processes that control the access of transcriptional machinery to the locus being transcribed.
So when you think about the two elements in a gene, think of a light (the bit of a gene that codes for proteins) and a dimmer (which controls how much RNA is made by the protein-coding bit)
The following is multiple choice question (with options) to answer.
What are the organized instructions within dna for making proteins called? | [
"clones",
"replicants",
"genomes",
"genes"
] | D | The DNA of a chromosome is encoded with genetic instructions for making proteins. These instructions are organized into units called genes . Most genes contain the instructions for a single protein. There may be hundreds or even thousands of genes on a single chromosome. |
SciQ | SciQ-3648 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
Macrophages, which can swallow and destroy old and dying cells, bacteria, or viruses, are large types of what cells? | [
"white blood cells",
"dendritic cells",
"red blood cells",
"white brain cells"
] | A | Macrophages are large WBCs that can also swallow and destroy old and dying cells, bacteria, or viruses. Below, a macrophage is attacking and swallowing two particles, possibly disease-causing pathogens ( Figure below ). Macrophages also release chemical messages that cause the number of WBCs to increase. |
SciQ | SciQ-3649 | organic-chemistry, atoms, intermolecular-forces, atomic-radius
Title: Range of distance for Van der Waals force Is there any range of distance between the nuclei of the atoms (in Angstrom, say between 4 to 12 Angstrom) within which there will be an occurrence of Van der Waals force (attraction) between them?
For example, say within a distance of 4 A between two atoms of same type, there will van der Waals attraction present. Can such a certainty be obtained? If two atoms are very far apart, then there will be not Van der Waals attraction between them, this is known. So my question is how close should the nuclei of two atoms be so that one can say with certainty that there will be Van der Waals attraction? Van der Waals force is due to interaction of two dipoles. It is never strictly zero, but it diminish very fast with distance.
It is common to look at VdW interaction at Van der Waals radius. The largest radius should be around 2.60 for Fr making the total distance between nuclei more than 4 A. Heavier elements will have larger radius, but heavier elements are not stable. Are we really interested in VdW force between two atoms that will decay in 10^-15 sec?
Also, by "4-12A" do you actually mean distance between nuclei or the surfaces of atoms (VdW radius A + VdW radius B + "4-12 Angstrom")? In the first case iodine has VdW = 2.15A, so nuclei interact on distances more than 4A. This is the distance between atoms of neighboring I2 molecules in the crystal. In the second case you will see some interaction, but it will be quite small.
The following is multiple choice question (with options) to answer.
What is the distance between the nuclei of two identical atoms bonded together called? | [
"atomic radius",
"bond radius",
"sleep radius",
"cycle radius"
] | A | Atomic radius is determined as the distance between the nuclei of two identical atoms bonded together. |
SciQ | SciQ-3650 | aqueous-solution
A final point is that some dissolved species can, in fact, be solvents on their own. In this case, the definition of whether the species is aqueous or liquid is not well-defined and usually depends on the context. For example, a 1:4 mixture of $\ce{MeOH}$ and $\ce{H_2O}$ is typically written as $\ce{MeOH{(l)} + {H_2O{(l)}}}$, but a solution where a small amount of $\ce{MeOH}$ (maybe used as a reactant) would be denoted $\ce{MeOH{(aq)}}$. This has to do with the definition of the thermodynamic activities of the species and if you have questions about this, there's probably someone else on here who is a better expert than I to explain.
The following is multiple choice question (with options) to answer.
What is the term for water that contains one or more dissolved substances? | [
"sediment solution",
"dilute solution",
"aqueous solution",
"evaporation solution"
] | C | We want to focus on solutions where the solvent is water. An aqueous solution is water that contains one or more dissolved substances. The dissolved substances in an aqueous solution may be solids, gases, or other liquids. Some examples are listed in the Table above . Other examples include vinegar (acetic acid in water), alcoholic beverages (ethanol in water), and liquid cough medicines (various drugs in water). |
SciQ | SciQ-3651 | human-biology, physiology, digestive-system, liver, bile
Both solid lines are subsets of bile acids, measured in the serum of cholecystectomized patients in a classic 1978 study. The shaded areas represent control (not cholecystectomized) patients. These measurements suggest that enterohepatic circulation still follows a pulsatile pattern after cholecystectomy.
The following is multiple choice question (with options) to answer.
Gall bladder removal surgery does not seriously affect digestion because ______ is still being produced. | [
"saliva",
"plasma",
"blood",
"bile"
] | D | Note Surgical removal is often advised for a gallbladder that becomes infected, inflamed, or perforated. This surgery does not seriously affect digestion because bile is still produced. |
SciQ | SciQ-3652 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
The hepatitis virus attacks only cells of what organ? | [
"kidney",
"lungs",
"brain",
"liver"
] | D | How Viruses Infect Specific Organs Specific glycoprotein molecules exposed on the surface of the cell membranes of host cells are exploited by many viruses to infect specific organs. For example, HIV is able to penetrate the plasma membranes of specific kinds of white blood cells called T-helper cells and monocytes, as well as some cells of the central nervous system. The hepatitis virus attacks only liver cells. These viruses are able to invade these cells, because the cells have binding sites on their surfaces that the viruses have exploited with equally specific glycoproteins in their coats. (Figure 3.19). The cell is tricked by the mimicry of the virus coat molecules, and the virus is able to enter the cell. Other recognition sites on the virus’s surface interact with the human immune system, prompting the body to produce antibodies. Antibodies are made in response to the antigens (or proteins associated with invasive pathogens). These same sites serve as places for antibodies to attach, and either destroy or inhibit the activity of the virus. Unfortunately, these sites on HIV are encoded by genes that change quickly, making the production of an effective vaccine against the virus very difficult. The virus population within an infected individual quickly evolves through mutation into different populations, or variants, distinguished by differences in these recognition sites. This rapid change of viral surface markers decreases the effectiveness of the person’s immune system in attacking the virus, because the antibodies will not recognize the new variations of the surface patterns. |
SciQ | SciQ-3653 | inorganic-chemistry, electrochemistry, corrosion
Title: Does iron rust because of impurities found in it (ex. carbon)? If we, theoretically, get a piece of ideally 100% pure iron and it is left in moist air? Will it rust? My understanding of iron rust is that the Iron itself becomes the ANODE and carbon impurities (as an example of impurities) are CATHODE, so if this cathode is not there will iron itself become anode and cathode and rust? Three substances are required to transform iron into rust : air (oxygen), water, and a impurity at the surface of the metal. If one of these substances is missing, iron will not rust. The whole operation occurs at the contact of the impurity and iron and it has an electric origin. The reduction occurs at the impurity working as a cathode. It is well described in N. N. Greenwood and E. Earnshaw, Chemistry of the Elements, Pergamon 1983, p.1250
The following is multiple choice question (with options) to answer.
A rusty bike has been left outside in damp weather too many times, so the iron in the metal parts have? | [
"rusted",
"decayed",
"eroded",
"melted"
] | A | Look at this rusty bike. It has been left outside in damp weather too many times, so the iron in the metal parts has rusted. Iron rusts when it combines with oxygen in the air. Iron rusting is an example of a chemical reaction. In a chemical reaction, substances change into entirely different substances. For example, the iron in the bike and the oxygen in the air have changed into rust. |
SciQ | SciQ-3654 | organs, skin, pain, injury
Title: Why Is The Toughness Of Skin Different On Different Parts Of The Body? My cat was licking my arm with his sandpaper like tongue. It hurt and the area he was licking was slightly smarting afterwards. However, when he licks the palm of my hand the feeling is rather ticklish and results in no pain during or after.
We can pick up sharp, prickly, abrasive objects with our hands (palms/fingers) and even rub against them and have little to no damage incurred. However, if we do the same with say the back of our hand we are more likely to be injured.
I thought maybe the skin is thicker in our palms and that is resulting in our palms being more resilient. But, our palms are so sensitive to touch that it makes me think the skin is thinner to allow the nerves closer access to our environment.
Why is there such a stark difference in different areas of skin on our body when it comes to feeling pain and being susceptible to injury from scrapes, bruises, cuts, etc? As dd3 said the density of mechanoreceptors dictates skin sensitivity to touch (also look at penfield map. It is a nice illustration of how different senses are mapped to the brain and to what extent each region is sensitive to stimulus). Skin thickness is also different in different regions. This article says that Dikkopf1 (a Wnt pathway antagonist) controls skin thickness.
The following is multiple choice question (with options) to answer.
What two layers is the skin made of? | [
"Blood and dermis",
"respiration and dermis",
"layers and dermis",
"epidermis and dermis"
] | D | Skin is made up of two layers, the epidermis on top and the dermis below. The tissue below the dermis is called the hypodermis, but it is not part of the skin. |
SciQ | SciQ-3655 | blood-circulation, immune-system
Title: Are there macrophages in the blood vessels and within the blood stream? Monocytes are phagocytes that "evolve" or "differentiate" into macrophages. I read that there are monocytes in the blood stream and vessels and that macrophages are found mainly in other tissues and in the lymphatic system.
My question: are there macrophages (and not merely monocytes) in the blood vessels and within the blood stream? And if there are, are they numerous there or sparse? Usually, monocytes and neutrophils are present(there are other cells like Lymphocytes and other leukocytes), the only time a macrophage will be present is when inflammation occurs, I suspect this is due to the large size of the macrophage, it would be difficult for it to travel in the bloodstream, as it is quite big, compared to the small size of a monocyte. During inflammation, vascular dilation and permeability increase, which makes it easier for cells and proteins to diffuse across the endothelium.
A source that macrophages are present in all tissues: https://www.researchgate.net/publication/227897252_Macrophages_in_the_embryo_and_beyond_Much_more_than_just_giant_phagocytes
A source that talks about all the leukocytes and lymphocytes present in the blood normally: http://www.histology.leeds.ac.uk/blood/blood_wbc.php
The following is multiple choice question (with options) to answer.
What are the three major types of blood vessels? | [
"arteries, veins, capillaries",
"arteries , pups , capillaries",
"arteries, capilaries, tubes",
"sculptures , veins , capillaries"
] | A | Blood vessels form a network throughout the body to transport blood to all the body cells. There are three major types of blood vessels: arteries, veins, and capillaries. All three are shown in Figure below and described below. |
SciQ | SciQ-3656 | thermodynamics, energy, earth, thermal-radiation
@Benjohn has given you the correct answer. Here is my take.
The ultimate heat provider of the earth ( except a small percentage of heat from the magma at the center of the earth) is the sun. It pours down at the surface about 1.2 kilowatts of energy per meter square ( which btw is directly used by solar panels). The same energy falls on the surface of the moon whose surface burns up during its daytime and freezes by black body radiation at night.
The earth is fortunate to have a gas atmosphere which mitigates the extremes of the possible temperatures that the ground would reach otherwise. An example of mitigation is what happens at the sea floor. Most of the energy is picked up by the water and the floor is kept at a steady temperature with small changes day and night in the first meters from the surface, depending on the season, radiating away with the black body radiation, but the body of water has such large heat capacity that variations are small.
The gas atmosphere is a more temperamental "blanket", its heat capacity depends on several gases , called green house gases from the bad impression that agricultural green houses work that way ( they do not, they work by inhibiting heat exchange by convection but that is another story, on which there is no controversy).
The main green house gas is water , H2O. It is worth contemplating this figure :
Solar irradiance spectrum above atmosphere and at surface. Extreme UV and X-rays are produced (at left of wavelength range shown) but comprise very small amounts of the Sun's total output power.
We see that H2O has the most absorption spectrum for infrared wavelengths, (which are the wavelengths of heat )and then comes CO2. Green house gases absorb both incoming and reflected from the surface of the earth infrared, and as most of the reflected wavelengths are in the infrared they act as a slowing down of the black body radiation that would finally leave the earth. As a blanket keeps a person warmer green house gases by playing ball with infrared radiation ( the wavelengths where heat is really transferred) keep the surface of the earth into a reasonable temperature for life, lucky us.
The following is multiple choice question (with options) to answer.
What is the name of the protective layer of gases that surrounds the earth and blocks harmful rays from the sun? | [
"the protector",
"the corona",
"the coma",
"the atmosphere"
] | D | The atmosphere protects living things from the Sun’s most harmful rays. Gases reflect or absorb the strongest rays of sunlight. Figure below models this role of the atmosphere. |
SciQ | SciQ-3657 | taxonomy
Title: Why are sponges sometimes not considered multicellular? I read somewhere (I can't find where) that there is no scientific consensus whether sponges should be considered multicellular organisms.
It seems I don't understand where is the line between unicellular and multicellular life.
I am not able to find a more elaborate explanation of that doubt. What are the reasons for it? Sponges are generally considered as colonial organisms because there is little cell specialization and little separation of function/role. All cells do pretty much the same thing; it looks more like a pile of individual cells than an actual multicellular organism. In reality it is a little bit in between.
In any case, what one wants to call multicellular or unicellular is a matter of definition and preferences. You cannot find the line between unicellular and multicellular because there is no such line that would not be very arbitrary and filled with special cases.
You can study a little more the physiology of sponges and then decide for yourself if it looks sufficiently like a multicellular organism or more like a colony of cells (a colonial organism).
The following is multiple choice question (with options) to answer.
What are colonies of cells stuck to a surface called? | [
"biofilms",
"membranes",
"membranes",
"cellular coating"
] | A | Prokaryotic cells are extremely small and have a variety of shapes. Most have flagella and a cell wall. They have several other cell structures as well. Their DNA exists as large and small loops. Some prokaryotes form biofilms, which are colonies of cells stuck to a surface. |
SciQ | SciQ-3658 | parasitology, infection
improved hygiene
adequate thermal processing of meat [2]
preventing contamination of animals (pigs and cattle) [3]
Differential diagnosis:
PCR [1, 4]
Hematoxylin-Eosin Staining [1]
References:
Mayta H, Talley A, Gilman RH, Jimenez J, Verastegui M, Ruiz M, Garcia HH, Gonzalez AE. Differentiating Taenia solium and Taenia saginata infections by simple hematoxylin-eosin staining and PCR-restriction enzyme analysis. J. Clin. Microbiol. 2000 Jan;38(1):133-7. PubMed PMID: 10618076. Cited text is from full text article available from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC86038/
Wikipedia contributors, "Taenia saginata," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Taenia_saginata&oldid=618599196 (accessed July 28, 2014).
Wikipedia contributors, "Taenia solium," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Taenia_solium&oldid=618599210 (accessed July 28, 2014).
Luis Miguel González, Estrella Montero, Leslie J. S. Harrison, R. Michael E. Parkhouse, and Teresa Garate. Differential Diagnosis of Taenia saginata and Taenia solium Infection by PCR. J. Clin. Microbiol. February 2000 vol. 38 no. 2 737-744
The following is multiple choice question (with options) to answer.
Trichomoniasis is cause by what type of pathogen? | [
"virus",
"protozoa",
"worm",
"bacteria"
] | B | STIs may be caused by several different types of pathogens, including protozoa, insects, bacteria, and viruses. For example: Protozoa cause an STI called trichomoniasis. The pathogen infects the vagina in females and the urethra in males, causing symptoms such as burning and itching. Trichomoniasis is common in young people. Pubic lice, like the one in Figure below , are insect parasites that are transmitted sexually. They suck the blood of their host and irritate the skin in the pubic area. |
SciQ | SciQ-3659 | star, galaxy, history, definition, stellar-structure
Title: Metallicity of Celestial Objects: Why "Metal = Non-metal"? Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium.
Note: The other elements may or may not be actual metals in the true sense of their defintion.
The following is multiple choice question (with options) to answer.
An increase in what, across the periodic table, explains why elements go from metals to metalloids and then to nonmetals? | [
"protons",
"electrons",
"neutrons",
"temperature"
] | B | The increase in electrons across the periodic table explains why elements go from metals to metalloids and then to nonmetals from left to right across the table. Look at period 2 in Figure below as an example. Lithium (Li) is a metal, boron (B) a metalloid, and fluorine (F) and neon (Ne) are nonmetals. The inner energy level is full for all four elements. This level has just one orbital and can hold a maximum of two electrons. The outer energy level is a different story. This level has four orbitals and can hold a maximum of eight electrons. Lithium has just one electron in this level, boron has three, fluorine has seven, and neon has eight. |
SciQ | SciQ-3660 | human-genetics
Title: In our 23 chromosome pairs, do the 2 members of the pair have distinct or virtually identical sequences? I understand that we have 46 DNA molecules in the nucleus of our cells, arranged in 23 pairs: 22 autosomal and 1 sex chromosome pairs.
I have read in different sources that the pairs contain nearly identical members, excluding any mutations. I have also read that the pairs contain 1 member we inherited from our mothers and 1 we inherited from our fathers, which are different due to inheritance.
This seems contradictory, given that genealogical companies match up on the differences on these chromosomes.
My understanding was that meiosis creates sperm and egg cells that each carry 23 chromosomes - they are haploids. During the first steps of meiosis that creates the reproductive cells we have a combining of the parent's chromosome pair from their parents to create 4 daughter cells, each independently viable, where the recombination of the chromosome pair has occurred at somewhat predictable spots (for you perhaps :-) ) and that these spots can be related to genes. It is this step that give us our genetic variation between siblings for example. A new person's DNA is partially formed from any one of these highly varied daughter cell possibilities.
Fertilization combines the reproductive cells to produce the 46 chromosome zygote with is again diploid.
I think this understanding supports the second interpretation that our chromosome pairs are not 2 nearly identical DNA molecules but are distinct.
Have I got this right? Is there a missing process or a misunderstanding in my interpretation? Homologous chromosomes (those that are paired up), excluding the sex pair are almost identical in size, shape and genes (members as you called them) present in them.
Genes determine traits and each homologous chromosome controls the same traits. The level of identity of a gene inside a population varies between genes. There are very conserved ones that do not change even between humans and yeast and others that vary alot event inside a species. This changes can be small in sequence length, a simple base (letter) swap or one deletion, and have a huge effect on the traits. This is how chimps and humans are very different but share 98.6% of their genome and humans are very similar and share 99.9% of their genome.
In summary, on the bigger scale homologous chromosomes are very similar (size, shape, traits inside), on the smaller scale homologous chromosomes have small changes that affect greatly.
The following is multiple choice question (with options) to answer.
How many pairs of chromosomes are in the human genome? | [
"21",
"23",
"24",
"13"
] | B | The human genome has 23 pairs of chromosomes located in the nucleus of somatic cells. Each chromosome is composed of genes and other DNA wound around histones (proteins) into a tightly coiled molecule. |
SciQ | SciQ-3661 | dna, human-genetics, dna-sequencing, genomics
Title: Is it possible to deduce facts about a person's parents just by studying his/her genome? As an example, suppose Anne had abusive parents. Is it theoretically possible to deduce this from her genome even if she didn't inherit this quality (of being an abusive parent)? It might seem pernickety but you often can't deduce from a genome; you can only infer from it. For many characteristics about a person, there are only rough, probabilistic associations between genotype and phenotype. Not one-to-one relationships.
You can take an educated guess that someone with a certain genotype could be a social person of European ethnicity with a low risk of psychosis, which might suggest things about their parents. But there are likely many genes that influence those characteristics and still more non-genetic factors. So you couldn't be certain.
For a factor like whether the persons parents had abusive personalities, I think the genetic differences would be so subtle (if existent) and there would be so many other factors (such as the habits and choices of the parents) that you would be very unlikely to be able to draw any conclusive associations. Articles and studies about linking human genetics with a person's characteristics are listed below. If any of the genes in question are linked with those characteristics then the parents of someone with the gene could possibly have those genes and characteristics too.
Personality types including belligerence, charisma, cynicism, housekeeping, lack of personality, obsessive-compulsive behaviour and gullibility.
Psychosis and Schizophrenia risks.
Ethnicity and European ethnicity, which in turn correlate with geographical location, language and certain phenotypes.
Height.
If anyone would like to suggest additions to that list, I'll happily add them.
The following is multiple choice question (with options) to answer.
What measure is resorted to by people who wish to screen out genetic abnormalities in the fetus? | [
"contraceptive use",
"stem cell therapy",
"prenatal testing",
"in vitro fertilization"
] | C | A genetic disorder that is caused by a mutation can be inherited. Therefore, people with a genetic disorder in their family may be concerned about having children with the disorder. Professionals known as genetic counselors can help them understand the risks of their children being affected. If they decide to have children, they may be advised to have prenatal (“before birth”) testing to see if the fetus has any genetic abnormalities. One method of prenatal testing is amniocentesis . In this procedure, a few fetal cells are extracted from the fluid surrounding the fetus, and the fetal chromosomes are examined. |
SciQ | SciQ-3662 | telescope, telescope-lens, diy
There's also an easier way. You could purchase a complete kit, like the Galileoscope:
http://galileoscope.org/
It's a 50 mm (2") f/10 refractor that has about the same performance like good binoculars. The price is very affordable (and very cheap for what it does). As a telescope and mirror maker, I was impressed by the quality of the achromat doublet objective that they provide (50 mm diameter, 500 mm focal length, f/10). For the price and the size, it is well made and well corrected, and punches well above its price category.
The kit comes with everything you need: all the lenses, the tube, various small parts, etc., including components for the ocular (eyepiece). Another nice thing is that you can swap its eyepiece for a standard 1-1/4" eyepiece used in a regular telescope (like a cheapie on Surplus Shed). Whoever designed this thing put some good thought in it. There are several different instruction documents on the site, that you can choose from.
My 9 and 12 year old sons put it together in an afternoon. It's that easy.
EDIT: What can you do with the Galileoscope?
Obviously, you can watch some of the planets. You'll see the two big equatorial belts on Jupiter, and the 4 galilean moons of Jupiter. Saturn's rings will be quite obvious. Venus will show a crescent - it will look just like the Moon, only much smaller.
You can watch the Moon, too. The big craters are quite visible in an instrument this size.
You can watch some of the deep space objects too. The Orion Nebula is quite visible actually. The Andromeda galaxy is somewhat visible from a place outside the city.
Double stars such as Albireo, which appear as single star to the naked eye, are easily split by a 50 mm aperture. Albireo is very pretty, and easy to see in a Galileoscope - an orange/blue double, easy and wide, very beautiful.
Mizar, one of the main stars in the Big Dipper, is also a double. This one is a lot more tight. I think you should be able to split it in a G-scope anyway.
http://www.synapses.co.uk/astro/bearings.html
The following is multiple choice question (with options) to answer.
Who built the first telescope? | [
"brahe",
"copernicus",
"newton",
"galileo"
] | D | Humans have been making and using magnifying lenses for thousands of years. The first telescope was built by Galileo in 1608. His telescope used two lenses to make distant objects appear both nearer and larger. |
SciQ | SciQ-3663 | human-biology, cell-biology, bacteriology, cell-membrane
Title: Can general soap kill bacteria? I have read that general soap can kill bacteria by opening holes in the bacterial membrane.
http://questions.sci-toys.com/node/90
However, I found some articles as well saying that it cannot.
http://goaskalice.columbia.edu/answered-questions/does-soap-kill-germs
There seems split answers among experts,
so I would like to know which one is correct.
Could anyone advise me?
Thanks. Soap kills nearly all the bacteria it comes into contact with by dissolving the bacterial membrane. Some viruses with protein coats can resist soap, but many viruses have similar membranous coats (like HIV) and are usually disrupted by soap. I'm sure it washes some away too, but to say they don't kill bacteria is misleading. In the end, though, they are gone.
Antibacterial soap with triclosan does not kill bacteria on contact and are no more effective than if they had no triclosan at all. That's actually a good thing since really using an antibiotic would probably accelerate antibiotic resistant bacteria which is a serious - probably catastrophic public health failure. A recent study showed that killing bacteria by soaking with triclosan took 9 hours to start showing an effect.
To achieve full sterility, surgeons bathe their gloves in iodine (see details in the comments below) and their instruments will be sterilized by heating them beyond the boiling point in an autoclave under pressure. That's useful when you are breaching the skin in surgery, but the skin needs some bacteria to be healthy long term and works well to fend off bacterial infections.
Your confusion seems to come from finding a page full of errors. Alice didn't really do her homework.
The following is multiple choice question (with options) to answer.
Water can be boiled to kill giardia and most other what? | [
"bacteria",
"pathogens",
"parasites",
"germs"
] | B | Different pathogens spread in different ways. Some pathogens spread through food. They cause food borne illnesses, which are discussed in a previous concept. Some pathogens spread through water. Giardia lamblia is one example. Water can be boiled to kill Giardia and most other pathogens. |
SciQ | SciQ-3664 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What do you call mixtures of ash and water that travel down river valleys? | [
"pollutants",
"debris",
"lahars",
"mud slides"
] | C | Lahars are mixtures of ash and water that travel down river valleys. On Mount St. Helens, the eruption melted glaciers. The water mixed with ash from the eruption and created tremendous lahars. The lahars raced down valleys and knocked out many bridges. |
SciQ | SciQ-3665 | polarity, isotope
M. Trefler and H. P. Gush found the dipole moment to be very small, i.e. $\mathbf{p}=(5.85\pm0.17)\times 10^{-4}~\mathrm{D}$. Hence to speak of deuterium protide or protium deuteride is a stretch.
Since the effect is quite small in $\ce{HD}$ already, one can probably assume it will not have a significant effect on the polarisation in other than symmetric diatomic molecules.
However, with isotopes a few notable applications can be achieved. One of the prime examples is “chiral acetate”, (R)-deuterotritioacetic acid $\ce{HDTC-COOH}$, which helped elucidate biosynthetic transformations. For a quite comprehensive, educational article see [4].
References
M. Trefler and H. P. Gush; Phys. Rev. Lett. 1968, 20, 703.
W. R. Thorson, J. H. Choi, and S. K. Knudson; Phys. Rev. A 1985, 31, 22.
(a) S. M. Blinder; J. Chem. Phys. 1960, 32, 105. (b) S. M. Blinder: The dipole moment of HD. http://hdl.handle.net/1811/7809 (c) J. Bradley Nelson and G. C. Tabisz;
Phys. Rev. Lett. 1982, 48, 1393. (d) G. Herzberg; Nature 1950, 166, 563. (e) etc. see google scholar
Addison Ault; J. Chem. Educ. 2003, 80 (3), 333.
The following is multiple choice question (with options) to answer.
Why do homonuclear diatomic molecules have zero dipole moment? | [
"no difference in electronegativity",
"no electrical attraction",
"no activation energy",
"at homeostasis"
] | A | A whole molecule may also have a separation of charge, depending on its molecular structure and the polarity of each of its bonds. If such a charge separation exists, the molecule is said to be a polar molecule (or dipole); otherwise the molecule is said to be nonpolar. The dipole moment measures the extent of net charge separation in the molecule as a whole. We determine the dipole moment by adding the bond moments in three-dimensional space, taking into account the molecular structure. For diatomic molecules, there is only one bond, so its bond dipole moment determines the molecular polarity. Homonuclear diatomic molecules such as Br2 and N2 have no difference in electronegativity, so their dipole moment is zero. For heteronuclear molecules such as CO, there is a small dipole moment. For HF, there is a larger dipole moment because there is a larger difference in electronegativity. When a molecule contains more than one bond, the geometry must be taken into account. If the bonds in a molecule are arranged such that their bond moments cancel (vector sum equals zero), then the molecule is nonpolar. This is the situation in CO2 (Figure 7.27). Each of the bonds is polar, but the molecule as a whole is nonpolar. From the Lewis structure, and using VSEPR theory, we determine that the CO2 molecule is linear with polar C=O bonds on opposite sides of the carbon atom. The bond moments cancel because they are pointed in opposite directions. In the case of the water molecule (Figure 7.27), the Lewis structure again shows that there are two bonds to a central atom, and the electronegativity difference again shows that each of these bonds has a nonzero bond moment. In this case, however,. |
SciQ | SciQ-3666 | immunology, pathology, pathophysiology
SRC
You can see in healthy phagocytes that through one of two pathways, protein antigens end up displayed on HLA molecules for cellular immunity to take over. Option B is that another cell like a macrophage detects distress signals from the infected cell and induces cell death in it through receptors or oxidative burst. In the case of Salmonella, HLA expression is down-regulated and oxidative burst can be inhibited so localized, infected antigen-presenting cells cant mount an effective response.
That's not to say everything is de-regulated early on. If you succeed in antigen presentation or innate killing (perhaps a non-pathogenic strain), you will resolve the infection as seen in the above figure: a combination of T-mediated killing, B-mediated killing, NK-mediated killing, and generalized inflammation.
In the chronic case, the pathogen will have escaped the primary immune response, but the system will attempt to continue to resolve the infection. This can lead to a number of things: cellular anergy, cellular hyperactivity, sequestration (see granuloma), chronic inflammation & tissue damage, and so forth. The following diagram is predicated upon viral infections but the immunology is largely similar:
SRC
There are changes to the system that are a result of over-exposure to antigen, and an inability to clear that stimulation. The best way to explain it is that chronic stimulation leads to both hyperactivity and suppression. The constant presence of effector molecules like TNF-a leads to a persistent state of tissue inflammation, which is bad for the tissue, but taken together with the persistent presence of antigen, this may lead to dysfunctional responses by lymphocytes (3).
A particularly virulent infection may be impossible for your immune system to clear without assistance, then, requiring the intervention of gram-negative antibiotics, for example.
The following is multiple choice question (with options) to answer.
The types of white blood cells that arrive at an inflamed site depend on the nature of what? | [
"genes",
"blood type",
"skin color",
"injury or infection"
] | D | capillaries cause swelling of the area, which in turn causes pain. Various kinds of white blood cells are attracted to the area of inflammation. The types of white blood cells that arrive at an inflamed site depend on the nature of the injury or infecting pathogen. For example, a neutrophil is an early arriving white blood cell that engulfs and digests pathogens. Neutrophils are the most abundant white blood cells of the immune system (Figure 17.9). Macrophages follow neutrophils and take over the phagocytosis function and are involved in the resolution of an inflamed site, cleaning up cell debris and pathogens. |
SciQ | SciQ-3667 | earth, rotation, temperature
Title: What contributes the most to the seasonal temperature variation? The seasonal temperature is ultimately due to the precession of the Earth around the axis. But what I'm curious about is... is it due more to the side experiencing winter being farther from the sun or is it more due to the fact that the days are shorter and the nights are longer? [ The earth is actually closer to the sun in the Northern hemisphere's winter. The seasonal temperature variation is predominantly due to the angle the earth makes with the sun. In the northern hemisphere in winter the angle is such that the earth is tilted with north pole away from the sun and the sunlight hitting the earth is spread over a much larger area than if it was pointed towards the sun. Due to this tilt the sun is also lower in the sky and has the effect shown in the 2nd figure.
The following is multiple choice question (with options) to answer.
In what season are temperature inversions more common? | [
"autumn",
"winter",
"summer",
"spring"
] | B | Sometimes air doesn’t mix in the troposphere. This happens when air is cooler close to the ground than it is above. The cool air is dense, so it stays near the ground. This is called a temperature inversion ( Figure below ). An inversion can trap air pollution near the surface. Temperature inversions are more common in the winter. Can you explain why?. |
SciQ | SciQ-3668 | meteorology, severe-weather
The lack of rich low-level moisture is due in large part to the lack of accessibility from warmer moisture sources, particularly the Gulf of Mexico; the Rockies provide a barrier to much of the moisture reaching further west.
As you note, parts of Wyoming and Montana do see supercells and tornadoes a bit more often... but on a good topographic map, fair parts of those states are east of the Continental Divide, and so still on an "upsloping" area and thereby not blocked by sinking regions which prevent full moisture progress. They're still less-tornado prone due to elevation and increased distance from moisture, but it does happen.
The desert southwest also does manage to get monsoon moisture sneaking around the terrain further south... but further north that monsoon moisture sees additional blocking by the more elevated terrain across Nevada and Utah. (And in the southwest, a different key ingredient in tornadic supercell development is typically missing in the summer monsoon: upper-air winds sufficient for supercell development)
The Pacific Coast does see a few occasional tornadoes. But from what I've seen, they typically form from smaller storms with much less classical and intense mesocyclones. As you mention, they're a bit more in line with cold-core setups, which usually produce weaker short-lived tornadoes than classic supercells of the Plains and on east. If you plug in the events you speak of into SPCs Severe Weather Events archive, [pick the date, then click Obs and Mesoanalysis on the left, then use the dropdowns to find various parameters]
you can see that CAPE was typically very meager (well short of 1000 J/kg) and the storm structure quite weak in reflectivity in comparison to a classic supercell, more indicative of such cold-core setups.
Capping inversions may be helpful to "keep the lid on the pot" if you have strong CAPE (and therefore quality moisture) and intense updrafts to erode the cap during the day. But as it is, there isn't enough moisture typically for the cap to be a positive factor.
The following is multiple choice question (with options) to answer.
Are thunderstorms more likely where the ground temperatures are extremely high or extremely low? | [
"extremely low",
"extremely high",
"somewhat high",
"somewhat low"
] | B | Thunderstorms grow where ground temperatures are extremely high. |
SciQ | SciQ-3669 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
What type of diseases in humans are caused by protozoa? | [
"protozoa diseases",
"dysentery",
"protist diseases",
"diarrhea"
] | C | Scientists are searching for ways to create controlled nuclear fusion reactions in order to produce safe nuclear power. Fusion involves only harmless, plentiful elements but requires extremely high temperatures. |
SciQ | SciQ-3670 | anatomy, ichthyology
Title: Is the fin of ray-finned fish live tissue or more similar to scales? In ray-finned fishes, are what exactly are the fins made of? Is it modified skin, dead tissue like scale or nail on humans, or something completely different? Can the fin heal? In teleosts, the fin skeleton is made of structures called lepidotrichia and actinotrichia, whereas homologue structures called ceratotrichia are found in the fins of the chondrichties. These are covered by living skin.
Lepidotrichia are calcified, segmented and branched bone-like rays that extend along the whole length of the fin, shaping it. Actinotrichia are mostly made of collagen and are found at the distal end of the ray, where they provide flexible support to the fin edge1.
Fins are able to regenerate, and this capability has been studied in a few different teleosts2,3,4.
References:
The following is multiple choice question (with options) to answer.
Shark teeth likely evolved from the jagged scales that cover their skin, called what? | [
"heterotroph scales",
"hook scales",
"pinworm scales",
"placoid scales"
] | D | Chondrichthyes: Cartilaginous Fishes The clade Chondrichthyes is diverse, consisting of sharks (Figure 29.11), rays, and skates, together with sawfishes and a few dozen species of fishes called chimaeras, or “ghost” sharks. ” Chondrichthyes are jawed fishes that possess paired fins and a skeleton made of cartilage. This clade arose approximately 370 million years ago in the early or middle Devonian. They are thought to be descended from the placoderms, which had skeletons made of bone; thus, the cartilaginous skeleton of Chondrichthyes is a later development. Parts of shark skeleton are strengthened by granules of calcium carbonate, but this is not the same as bone. Most cartilaginous fishes live in marine habitats, with a few species living in fresh water for a part or all of their lives. Most sharks are carnivores that feed on live prey, either swallowing it whole or using their jaws and teeth to tear it into smaller pieces. Shark teeth likely evolved from the jagged scales that cover their skin, called placoid scales. Some species of sharks and rays are suspension feeders that feed on plankton. |
SciQ | SciQ-3671 | neuroscience, neurophysiology, sensation, hearing, human-ear
Title: Why/how does exposure to noise cause cochlear hair-cell loss? I am trying to understand why listening to loud music - e.g. concerts or earphones at high volume damages hearing.
According to the National Institute on Deafness the cause is physical.
Most NIHL is caused by the damage and eventual death of these hair
cells. Unlike bird and amphibian hair cells, human hair cells don’t
grow back. They are gone for good.
But I don't understand why/how would noise - which should basically lead to higher amplitude waves in the basilar membrane, induce damage and death of these hair cells? There are a number of pathophysiological mechanisms that are thought to underlie noise-induced hearing loss:
Mechanical damage to the delicate cells and supporting structures of the organ of Corti;
Reduced blood flow to the inner ear;
Intense metabolic activity, which increases mitochondrial free radical formation.
Reactive oxygen species (ROS) are highly reactive. They are essential for mitochondrial function to generate energy. However, too many of them damage cellular lipids, proteins, and DNA, and upregulate apoptotic pathways. The observed impaired blood flow to the cochlea can enhance the toxic effects of ROS. Mechanical damage to the delicate hairs and membranes of the hair cells reduces their ability to converge acoustical energy into potential differences.
References
- Le Prell et al., Hear Res (2007); 226(1-2): 22–43
- Kurabvi et al., Hear Res (2017); 349: 129-37
The following is multiple choice question (with options) to answer.
In the human ear, sound waves cause the stapes to press against what? | [
"Idea Window",
"oval window",
"yellow window",
"shaped window"
] | B | Figure 36.14 In the human ear, sound waves cause the stapes to press against the oval window. Vibrations travel up the fluid-filled interior of the cochlea. The basilar membrane that lines the cochlea gets continuously thinner toward the apex of the cochlea. Different thicknesses of membrane vibrate in response to different frequencies of sound. Sound waves then exit through the round window. In the cross section of the cochlea (top right figure), note that in addition to the upper canal and lower canal, the cochlea also has a middle canal. The organ of Corti (bottom image) is the site of sound transduction. Movement of stereocilia on hair cells results in an action potential that travels along the auditory nerve. |
SciQ | SciQ-3672 | reaction-mechanism, kinetics
Title: Can we interpret the "extent of reaction" as the number of reactions that happened? Consider this reaction:
$$\ce{\alpha\ A + \beta\ B -> \omega\ C + \delta\ D}$$
Where $\ce A$ and $\ce B$ are the reactants, $\ce C$ and $\ce D$ are the products, and $ \alpha, \beta, \omega, \delta$ their respective stoichiometric constants
We can then define the extent of reaction at instant $t$ as: $\xi (t)$.
My question is: can we interpret the extent of reaction as the number of reactions that happened at an instant $t$ considering that say, for reactant $\ce A$ at instant $t$: $$n_{t}(\ce A) = n_{i}(\ce A) - \alpha\times \xi(t)$$ If I understand this correctly you want to measure $\ce A$ to infer the extent of reaction. I think you should have started with mathmatically defining the extend of reaction:
$$\xi(t) = \left[\frac{n_i(\ce A) -n_t(\ce A)}{n_i(\ce A)}\right]\tag 1$$
Where $n_t$ is the concentration at a given time $t$. Here $n_i(\ce A) -n_t(\ce A)$ gives the consumed concentration of $\ce A$ after time $t$ which is normalized by the initial concentration to yield an extent of conversion.
The following is multiple choice question (with options) to answer.
What is the term for proportion of amount of product actually produced in a chemical reaction versus predicted amount ? | [
"calculus yield",
"percent impact",
"decrease yield",
"percent yield"
] | D | Chemical reactions in the real world don’t always go exactly as planned on paper. In the course of an experiment, many things will contribute to the formation of less product than would be predicted. Besides spills and other experimental errors, there are usually losses due to an incomplete reaction, undesirable side reactions, etc. Chemists need a measurement that indicates how successful a reaction has been. This measurement is called the percent yield. |
SciQ | SciQ-3673 | meteorology, geomorphology, climatology, atmospheric-circulation
Source Commons Wikipedia.
The cold waters near the ocean surface results in a cool, stable coastal atmosphere. In this region, evaporation from the ocean is reduced and produces extremely low rainfall over land. Precipitation is limited to morning fog and produces some of the driest ecosystems on Earth. The Atacama desert is the best example of such environment with average rainfalls of 15 mm/year (the driest non-polar region). In some areas, they are trying to take advantage of the little moisture the fog (Camanchaca) brings to establish some agricultural zones. The fog droplets are too small (1-40 micrometers) to form water drops and precipitate, so they use fog-catchers to collect moisture from the fog.
Source: newatlas.com
The following is multiple choice question (with options) to answer.
What creates wet and dry zones at different latitudes? | [
"global air currents",
"jet stream",
"trade winds",
"horse latitudes"
] | A | Temperature falls from the equator to the poles. Global air currents create wet and dry zones at different latitudes. They also create global winds. |
SciQ | SciQ-3674 | Of each score from any number, of the distribution we not just use the popular mean... Gives a measure of dispersion indicates the degree to which numerical data to. It also works in percentage terms as a percentage of some starting level which looks like.. Is calculated as the square root of the highest and smallest values the difference of each observation from mean.. Another term for these statistics is measures of dispersion like range, R, of deviations... Are useful measures are useful please provide specific applications in which one measure! Each value from the mean or average determining the variation between each data point relative to mean... Are a measure of dispersion indicates the degree to which individual items in a series other is Graphical method are! Are on the scale of measurement how spread out the data score from any number R of. And minimum values on the number line less intuitive hand, relative measures of spread between... Other measures of dispersion in the past, we will discuss the standard deviation, and!
The following is multiple choice question (with options) to answer.
What term is used to describe the total spread of values in a sample? | [
"range",
"variety",
"axis",
"scale"
] | A | Many samples have a lot of variation in measurements. Variation can be described with a statistic called the range. The range is the total spread of values in a sample. It is calculated by subtracting the smallest value from the largest value. |
SciQ | SciQ-3675 | agriculture
The primary cereals for making bread are wheat and rye, while barley and oats may be mixed in. Historically significant portions of the rural population of Europe were sustained by cereal-based food in the form of gruel and porridge rather than by bread, especially prior to the introduction of the potato. Barley can be consumed in the form of pearl barley and groats and oats in the form of oatmeal. Especially in cool and humid climates not very suitable for cultivating wheat and rye, oats were once commonly cultivated and consumed. When Samuel Johnson wrote his dictionary, he famously defined oats as: "A grain which in England is generally given to horses, but in Scotland supports the people." A major historical and modern use of barley has been as malted barley, the main ingredient in beer brewing.
In the case of Finland it is interesting to note how late the transition from slash-and-burn agriculture to the use of permanent fields occurred. According to Teija Alenius, Environmental change and anthropogenic impact on lake sediments during the Holocene in the Finnish − Karelian inland area, Ph.D. thesis, University of Helsinki, 2007 (online)
The following is multiple choice question (with options) to answer.
Fermentation—of grains to produce beer, and of fruits to produce wine—is an ancient art that humans in most cultures have practiced for how long? | [
"years",
"decades",
"eons",
"millennia"
] | D | Fermentation—of grains to produce beer, and of fruits to produce wine—is an ancient art that humans in most cultures have practiced for millennia. Wild yeasts are acquired from the environment and used to ferment sugars into CO2 and ethyl alcohol under anaerobic conditions. It is now possible to purchase isolated strains of wild yeasts from different wine-making regions. Louis Pasteur was instrumental in developing a reliable strain of brewer’s yeast, Saccharomyces cerevisiae, for the French brewing industry in the late 1850s. This was one of the first examples of biotechnology patenting. Many secondary metabolites of fungi are of great commercial importance. Antibiotics are naturally produced by fungi to kill or inhibit the growth of bacteria, limiting their competition in the natural environment. Important antibiotics, such as penicillin and the cephalosporins, are isolated from fungi. Valuable drugs isolated from fungi include the immunosuppressant drug cyclosporine (which reduces the risk of rejection after organ transplant), the precursors of steroid hormones, and ergot alkaloids used to stop bleeding. Psilocybin is a compound found in fungi such as Psilocybe semilanceata and Gymnopilus junonius, which have been used for their hallucinogenic properties by various cultures for thousands of years. As simple eukaryotic organisms, fungi are important model research organisms. Many advances in modern genetics were achieved by the use of the red bread mold Neurospora crassa. Additionally, many important genes originally discovered in S. cerevisiae served as a starting point in discovering analogous human genes. As a eukaryotic organism, the yeast cell produces and modifies proteins in a manner similar to human cells, as opposed to the bacterium Escherichia coli, which lacks the internal membrane structures and enzymes to tag proteins for export. This makes yeast a much better organism for use in recombinant DNA technology experiments. Like bacteria, yeasts grow easily in culture, have a short generation time, and are amenable to genetic modification. |
SciQ | SciQ-3676 | newtonian-mechanics, forces, fluid-dynamics, reference-frames, drag
Title: Is drag force in the direction of particle motion or opposite to motion? Suppose water is flowing in horizontal direction (positive $x$-direction) and a particle immersed in that water is also moving in the same direction.
In this case, is the drag force $F_D$ in the direction of particle motion or opposite to it?
I get from wikipedia that drag force is a frictional force and hence is opposite to particle motion, but then what is the force that is making the particle move. Because in one journal paper, I see that drag force $F_D$ is shown as force in the direction of particle motion.
This is a sketch from the paper, you can see that flow velocity and drag force are both in the same direction. Drag force opposes the motion of a body relative to the surrounding fluid. In this case the surrounding fluid moves to the right and relative to that the solids move to the left.
The drag force is opposing the motion to the left, hence it is towards the right. The solids are being swept away by the fluid.
The following is multiple choice question (with options) to answer.
In which direction does water travel? | [
"backwards",
"downhill",
"uphill",
"northwest"
] | B | After a heavy rain, you may find puddles of water standing in low spots. The same principle explains why water collects in ponds and lakes. Water travels downhill, so a depression in the ground fills with standing water. A pond is a small body of standing water. A lake is a large body of standing water. Most lakes have freshwater, but a few are salty. The Great Salt Lake in Utah is an example of a saltwater lake. |
SciQ | SciQ-3677 | mathematical-models, population-dynamics
Title: Range of feasible coefficients in an unlimited growth model If you are given an unlimited growth model in the form:
$\frac {dP(t)}{dt} = k P(t)$
Obviously the population growth would never be unlimited, but let's presume for the moment that we are introducing a species into an environment where there is the possibility for unlimited growth, at least on for a given time -- i.e. invasive species.
$k$ is some rate of growth of the population at time $t$, denoted by $P(t)$
What are some feasible values of $k$? In other words, if a number is way above or way below $k$, where would I know that the research I am reading is preposterously off-base?
I am sure it is different for different types of animals, including mammals, birds, bacteria, etc. A solid limit: k must be greater than zero. Unless you're talking about some cannibalistic species or something that isn't suited to the model at all.
As long as the species is productive in the new environment: k is greater than 1. The population is probably growing or again you probably won't be using an exponential growth model.
As mentioned before you would need to know the species for more information. But if you look at generation times and litter sizes:
Some bacterial generation times (from here) range from 10 to
2000 minutes (33 hours). So that is $k=2$ per generation time. Per
day you're looking at a lower bound of 2 per day and an upper bound
of $k=2^{14}=10^{43}$ per day.
Mice are something like 12 week generation time and a litter of 10
giving something like $k=10^{10}$ per year.
Elephants are one young every 25 years. So $k=16$ per century or so.
Of course this is all based on gross assumptions. But you're looking for guidelines for a unrealistic model so hopefully they'll do.
The following is multiple choice question (with options) to answer.
The largest population size that can be supported in an area without harming the environment is referred to as what? | [
"population shift",
"population density",
"containing capacity",
"carrying capacity"
] | D | At what population size does growth start to slow in the logistic model of growth? That depends on the population’s carrying capacity (see Figure above ). The carrying capacity (K) is the largest population size that can be supported in an area without harming the environment. Population growth hits a ceiling at that size in the logistic growth model. |
SciQ | SciQ-3678 | elementary-particles
A textbook on solid state physics can help elucidate further properties of solids for you.
A textbook on the Standard Model of particle physics would be useful to catalog the known point-particles like electrons, muons, gluons, etc.
Finally, you mentioned "elements". By this, I believe you mean the different types of atoms, e.g., the element hydrogen, the element copper, etc. The different elemental atoms have different properties due to their differing number of protons, e.g. hydrogen has 1 proton, copper has 29 protons. In this matter, too, a textbook on chemistry will be useful to you.
Cheers.
The following is multiple choice question (with options) to answer.
What are the smallest particles of elements that maintain their unique properties? | [
"electrons",
"atoms",
"molecules",
"protons"
] | B | A: The discovery of particles smaller than atoms doesn’t mean that we should scrap the entire theory. Atoms are still known to be the smallest particles of elements that have the properties of the elements. Also, it is atoms—not particles of atoms—that combine in fixed proportions in compounds. Instead of throwing out Dalton’s theory, scientists have refined and expanded on it. |
SciQ | SciQ-3679 | species-identification
Title: What species is this worm? I was at the park lying on the grass and its the third time I have seen them, I used to think they were parasites when I was like 7. It is the very small brown worm on the green leaf. It moves by squiggling. It comes in different colors but same size.
http://postimg.org/image/ea3x2nw95/
http://postimg.org/image/zfawh9pr1/ For me it looks like an inchworms which are the larvae of geometer moth or Geometridae.
By your picture it is almost impossible to see of which type it is.
I took picture of one in Switzerland (but likely not the same as yours).
Full resolution here: https://flic.kr/p/utFsiU
The following is multiple choice question (with options) to answer.
Where does the christmas tree worm live? | [
"northeast coral reefs",
"Atlantic shoreline",
"tropical coral reefs",
"rainforests"
] | C | It is actually the Yellow Christmas tree worm. These animals are colorful, and can be red, orange, yellow, blue, and white. The Christmas tree worm lives on tropical coral reefs throughout the world. The Christmas tree worm's plumes are used for feeding and respiration. These worms use their plumes to catch plankton and other small particles passing in the water. Cilia then pass the food to the worm's mouth. |
SciQ | SciQ-3680 | hydrology, rivers, geomorphology
Mountain ranges are often formed from orogeny, where tectonic plates collide. Rivers starts at high altitude, radiating out in all directions from mountains, but as collisions in the present continental settings are often on the rim of large plates (e.g Andes, Alps, Himalaya), and the rivers can't cross the range, it will have to travel the whole continental plate to reach ocean level. In the case of Asia, most large rivers starts in Himalaya (or other tectonic active regions, as Altai), in Europe large rivers starts in the Alps. In Africa, they start in the tectonic active rift zone.
This map shows the ocean drainage dividers. The border between the drainage areas are the line where rivers start.
The following is multiple choice question (with options) to answer.
What are biomes that occur where a river, a source of fresh water, meets the ocean called? | [
"rapids",
"sediments",
"waterways",
"estuaries"
] | D | Estuaries: Where the Ocean Meets Fresh Water Estuaries are biomes that occur where a river, a source of fresh water, meets the ocean. Therefore, both fresh water and salt water are found in the same vicinity; mixing results in a diluted (brackish) salt water. Estuaries form protected areas where many of the offspring of crustaceans, mollusks, and fish begin their lives. Salinity is an important factor that influences the organisms and the adaptations of the organisms found in estuaries. The salinity of estuaries varies and is based on the rate of flow of its freshwater sources. Once or twice a day, high tides bring salt water into the estuary. Low tides occurring at the same frequency reverse the current of salt water (Figure 20.30). |
SciQ | SciQ-3681 | transcription, translation
Ralston, A. (2008) Operons and prokaryotic gene regulation. Nature Education
From Genes to Genomes: Concepts and Applications of DNA Technology
Molecular cell biology
Analysis of Genes and Genomes
The following is multiple choice question (with options) to answer.
What continuously monitors and repairs its genetic material? | [
"cells",
"nucleolus",
"ova",
"proteins"
] | A | |
SciQ | SciQ-3682 | geophysics, plate-tectonics
Title: Equatorial bulge and tectonic plates It is well known that the Earth is not a sphere, but rather it bulges at the equator. Also it is well known that the Earth's crust is composed of 7 or 8 (depending on definition) major tectonic plates, which are able to move on top of the asthenosphere, the upper layer of the Earth's mantle.
Due to the equatorial bulge, it would seem as though plates near the equator should not be able to drift away from the equator, and plates away from the equator should not be able to drift near the equator, since they will not be of the right shape to fit over these portions of the Earth. So how are the plates able to drift to and from the equator when the surface of the Earth is shaped differently there? The plates are not as rigid as you think. You seem to be imagining the situation as something like this: I boil an egg and take the shell off in pieces, but I can't take a piece of shell from the end and make it lay flat on the side of the egg. However, rock is not that rigid on scales of thousands of kilometres and millions of years (I don't think there exists any material which would be that rigid). Also, Earth's equatorial bulge is tiny relative to its diameter -- less than 50km. Tectonic plates move very slowly, and there is plenty of time for them to deform as they move.
The following is multiple choice question (with options) to answer.
What are the large segments of the earth’s crust that ordinarily move very slowly? | [
"lava plates",
"ocean plates",
"tectonic plates",
"distinct plates"
] | C | Tectonic plates are large segments of the Earth’s crust that move slowly. Suppose that one such plate has an average speed of 4.0 cm/year. (a) What distance does it move in 1 s at this speed? (b) What is its speed in kilometers per million years? 10. (a) Refer to Table 1.3 to determine the average distance between the Earth and the Sun. Then calculate the average speed of the Earth in its orbit in kilometers per second. (b) What is this in meters per second?. |
SciQ | SciQ-3683 | mineralogy, hydrogeology, mars
Despite active transport into Earth’s mantle, water has been present on our planet’s surface for most of geological time. Yet water disappeared from the Martian surface soon after its formation. Although some of the water on Mars was lost to space via photolysis following the collapse of the planet’s magnetic field, the widespread serpentinization of Martian crust suggests that metamorphic hydration reactions played a critical part in the sequestration of the crust. Here we quantify the relative volumes of water that could be removed from each planet’s surface via the burial and metamorphism of hydrated mafic crusts, and calculate mineral transition-induced bulk-density changes at conditions of elevated pressure and temperature for each. The metamorphic mineral assemblages in relatively FeO-rich Martian lavas can hold about 25 per cent more structurally bound water than those in metamorphosed terrestrial basalts, and can retain it at greater depths within Mars. Our calculations suggest that in excess of 9 per cent by volume of the Martian mantle may contain hydrous mineral species as a consequence of surface reactions, compared to about 4 per cent by volume of Earth’s mantle. Furthermore, neither primitive nor evolved hydrated Martian crust show noticeably different bulk densities compared to their anhydrous equivalents, in contrast to hydrous mafic terrestrial crust, which transforms to denser eclogite upon dehydration. This would have allowed efficient overplating and burial of early Martian crust in a stagnant-lid tectonic regime, in which the lithosphere comprised a single tectonic plate, with only the warmer, lower crust involved in mantle convection. This provided an important sink for hydrospheric water and a mechanism for oxidizing the Martian mantle. Conversely, relatively buoyant mafic crust and hotter geothermal gradients on Earth reduced the potential for upper-mantle hydration early in its geological history, leading to water being retained close to its surface, and thus creating conditions conducive for the evolution of complex multicellular life.
does serpentinization just refer to the formation of some hydrated minerals that happen to be of a class that is historically been referred to as serpentinite or it's subgroup
The following is multiple choice question (with options) to answer.
Which process causes rocks at the earth's surface to change form? | [
"weathering",
"remodeling",
"eroding",
"bleaching"
] | A | Weathering changes solid rock into sediments. Sediments are different sizes of rock particles. Boulders are sediments; so is gravel. At the other end, silt and clay are also sediments. Weathering causes rocks at the Earth’s surface to change form. The new minerals that form are stable at the Earth’s surface. |
SciQ | SciQ-3684 | thermodynamics, energy, combustion
Title: What is change in internal energy of a system in which combustion occurs at constant temperature? We got a question in a test, in which we were asked which system has zero change in internal energy and it had an option which was combustion of methane at constant temperature. I imagined this to be a situation in which the combustion is carried out in a system, where the change in internal energy of system due to heat released, is cancelled by the work done by the system. The reason why I thought of this is because of the formula,
∆U=nCv∆T,
But this was wrong. When I asked my sir how this was wrong, he was not able to say why the ans using above stated formula is wrong. He tried giving me a logical explanation in which he said that a small part of the system releases heat which is used by the remaining part for it's combustion, thus the total temperature remains constant. but I am unable to understand why we choose to only study a part of the system while we have the entire system. It makes no sense to me. Could someone please explain how my sir's explanation is valid here and why the formula is wrong to use here? The change in internal energy of a reaction mixture is a function not only of the temperature change but also of the changes in the amounts of reactants and products in the mixture. This is because energy is consumed and released when we break- and make chemical bonds. The equation you wrote for the internal energy change applies only to a pure species or to a mixture of constant chemical composition. The occurrence of chemical reactions causes a change in the internal energy even at constant temperature.
The following is multiple choice question (with options) to answer.
Chemical reactions always involve energy. when methane burns, for example, it releases energy in the form of what? | [
"movement and light",
"heat and light",
"heat and movement",
"light and sound"
] | B | Chemical reactions always involve energy. When methane burns, for example, it releases energy in the form of heat and light. Other chemical reactions absorb energy rather than release it. |
SciQ | SciQ-3685 | neuroscience, neurophysiology, memory, cognition
Title: What are the advantages of forgetting? How forgetting things is helpful for the brain or the human body biologically? This web page
After some moment of being rude, selfish, or weak, either we are able to put it behind us, or the person who suffered at the result of our imperfection moves on. The reason for this is our ability to forget about it. We forget not because we have an imperfect hippocampus (our brain’s memory organ); it's actually an evolved solution. The ability to lose information allows new information to come in that is more relevant, more pertinent to an ongoing reality. Forgetting allows us to update.
and this Huffington post article
According to a study in Nature, our awareness is limited to only three or four objects at any given time. To be able to think at your highest level, you therefore must be very efficient at filtering out all of the background noise: Your racing thoughts, the ringing phone, your neighbor’s barking dog, and the list goes on.
The Nature study found that when participants were asked to “hold in mind” certain objects while ignoring others, there are significant variations in how well each of us can keep irrelevant objects out of our awareness.
The researchers concluded that our memory capacity is therefore not simply about storage space, but rather “how efficiently irrelevant information is excluded from using up vital storage capacity.”
provide some backgrounds. Short answer
It has been shown that loss of long-term memories may enhance the retrieval of others. Short-term working memory is explicitly designed to be volatile and non-lasting. However, there are many other types of memories where memory loss may not be explicitly beneficial, or even outright debilitating such as in the case of Alzheimer's or stroke.
Background
First off all, there are many types of memories, including sensory memory, motor memory, short-term (working) memory, long-term memory, explicit & implicit memory, declarative & procedural memory and so on. Hence, because the question is quite broad, I will focus on long-term memory, short term-memory and sensory memory to discuss that memory loss can be beneficial, neutral, or detrimental.
The following is multiple choice question (with options) to answer.
Alzheimers disease is associated with memory loss in what group of people? | [
"immigrants",
"prehistoric",
"juveniles",
"elderly"
] | D | One useful application of PET scanning is in the diagnosis of Alzheimer’s disease. This debilitating condition associated with memory loss primarily occurs in elderly individuals. A protein known as beta-amyloid gradually forms deposits, or plaques, in the brain. Severe memory loss and impaired movement appear to be direct results of the plaque growth. |
SciQ | SciQ-3686 | geophysics, climatology, core
Title: How does the rotation of Earth's inner core influence climate? In the recent paper published in Nature that sugests a 60-70 years inner core rotation cycle, it is said:
Interestingly, the same multidecadal periodicity is also well observed
in the Earth’s climate system, especially the global mean
temperature and sea level rise.
The assertion quotes this paper published in 1994.
Is this multidecadal climate cycle well accepted among climatologists? It was maybe attributed to other causes than the inner core rotation before this study?
How can then the inner core rotation influence climate?
-Yang, Y., Song, X. (2023): "Multidecadal variation of the Earth’s inner-core rotation." Nature Geoscience. https://doi.org/10.1038/s41561-022-01112-z
-Schlesinger, M., Ramankutty, N. (1994) "An oscillation in the global climate system of period 65–70 years." Nature 367, 723–726. https://doi.org/10.1038/367723a0 I have four things to say regarding this:
The paper is far too new. I'm not saying the first paper is wrong (it is in fact rather interesting), but having been published yesterday, it is far too new to be used as the basis for anything. Publication in a peer-reviewed journal is where science starts rather than ends. Wait a bit for the scientific community to confirm or reject the claims in this paper.
The two effects might be completely unrelated.
If they are related, you might be confusing cause and effect. It could be that whatever causes the climate oscillations in turn causes the oscillations in the inner core's rotation rate.
What the authors of the paper in question are reporting to have observed is a small differential rotation between the mantle+crust and the inner core. It could well be that the inner core rotates much more smoothly than does the mantle+crust. In other words, they're seeing variations in the rotation rate of the mantle+crust.
The following is multiple choice question (with options) to answer.
What global cycle takes place on, above, and below earth’s surface? | [
"water wheel",
"water flow",
"aqua cycle",
"water cycle"
] | D | Water on Earth is billions of years old. However, individual water molecules keep moving through the water cycle. The water cycle is a global cycle. It takes place on, above, and below Earth’s surface, as shown in Figure below . |
SciQ | SciQ-3687 | identification, minerals
Title: How can chemists distinguish pure chemical element specimens that look almost "the same" as well as what deposit is what in a multimineral mined rock? As a non chemist I am most often charmed when visiting Wikipedia articles of chemical elements and see images of very pure specimens of element after element, proton by proton, and often also metal cube specimen made from smithing similar pure deposits.
The wiki article Periodic table allows me to do so easily; here are some elements I found looking almost the same and don't think I personally could distinguish between them without some instrument:
molybdenum and manganase
titanium and chromium
rutenium and cadmium
sodium and aluminium
silicone and germanium
The following is multiple choice question (with options) to answer.
Why are two different minerals considered different though they have the same chemical composition? | [
"different linear structures",
"different crystal structures",
"different molecular structures",
"different rods structures"
] | B | Sometimes two different minerals have the same chemical composition. But they are different minerals because they have different crystal structures. Diamonds are very valuable as gemstones because they are very pretty and very hard. Graphite is the “lead” in pencils. It's not hard at all! Amazingly, both are made just of carbon. Compare the diamond with the pencil lead ( Figure below ). Why are they so different? The carbon atoms in graphite bond to form layers. The bonds between each layer are weak. The carbon sheets can just slip past each other. The carbon atoms in diamonds bond together in all three directions. This strong network makes diamonds very hard. |
SciQ | SciQ-3688 | human-biology, genetics, pathology, chromosome, history
Title: How was the Huntington's disease gene's location found? I read in the book "Why we get sick." by Nesse and Williams that:
Steady detective work and fabulous luck have enabled geneticists to
pinpoint the Huntington's gene on the short arm of chromosome 4.
I want to know what was the "detective" work and the fabulous luck - the whole story of the discovery of the location of the gene. A Google search for "Huntingtons disease gene discovery" yielded this page at the Nature Education Scitable website. The following citations are provided regarding the molecular basis of HD:
Huntingtin (HTT) was the first disease-associated gene to be
molecularly mapped to a human chromosome (Gusella et al., 1983)2. Ten
years later, scientists identified the DNA sequence and determined the
precise nature of the HD-associated mutation in HTT (MacDonald et al.,
1993).
Gusella et al. used restriction fragment length polymorphism (RFLP) analysis to locate a RFLP marker linked to Huntington's disease on chromosome 4. From the introduction of their paper:
We have now identified an anonymous DNA fragment from human chromosome
4 that detects two different RFLPs in a HindIII digest of human
genomic DNA. This polymorphic DNA marker shows close genetic linkage
to the Huntington's disease gene in two separate families, although a
different haplotype of the marker segregates with the Huntington's
disease gene in each family. We infer that the Huntington's disease
locus resides on human chromosome 4.
Further details given in the paper might justify the description given in the question. "Fabolous luck" could refer to the discovery or availability of suitable families and pedigrees for the genetic studies. The "steady detective work" would be the genetic mapping and fieldwork required to establish the link. The following quotes describe some of the efforts spent on the project:
The following is multiple choice question (with options) to answer.
What type of mapping is critical for identifying the location of genes that cause genetic diseases? | [
"linkage mapping",
"interaction mapping",
"diagnostic mapping",
"chemical mapping"
] | A | Determining recombination frequencies between genes located on the same chromosome allows a linkage map to be developed. Linkage mapping is critical for identifying the location of genes that cause genetic diseases. |
SciQ | SciQ-3689 | hematology, red-blood-cell
So, menstrual "blood" is a combination of sloughed off stromal and glandular tissue, broken down vascular cells and blood, and, no, it is not highly oxygenated (it's kind of darker than normal blood. It doesn't carry any "decoded DNA". It's basically a waste product at this point, dead, dying and no longer functional tissue.
Virgin's flow is just as dead as non-virgin's flow. Cultures obtained at hysterectomy indicate that the endometrial cavity is normally sterile. The major difference between a virgin and a non-virgin is that the possibility of infection of endometrial tissue exists in non-virgins.
Of course myths will arise around menstrual flow. After all, when it was alive, it was the medium for implantation of a blastocyst. But they are just myths.
Endometrium Histology
Infections as a Cause of Infertility
The following is multiple choice question (with options) to answer.
When menstrual periods become less frequent and finally cease; this is called? | [
"menopause",
"metabolic",
"climax",
"hormonal imbalance"
] | A | Which of the following statements about the menstrual cycle is false? a. Progesterone levels rise during the luteal phase of the ovarian cycle and the secretory phase of the uterine cycle. Menstruation occurs just after LH and FSH levels peak. Menstruation occurs after progesterone levels drop. Estrogen levels rise before ovulation, while progesterone levels rise after. Menopause As women approach their mid-40s to mid-50s, their ovaries begin to lose their sensitivity to FSH and LH. Menstrual periods become less frequent and finally cease; this is menopause. There are still eggs and potential follicles on the ovaries, but without the stimulation of FSH and LH, they will not produce a viable egg to be released. The outcome of this is the inability to have children. The side effects of menopause include hot flashes, heavy sweating (especially at night), headaches, some hair loss, muscle pain, vaginal dryness, insomnia, depression, weight gain, and mood swings. Estrogen is involved in calcium metabolism and, without it, blood levels of calcium decrease. To replenish the blood, calcium is lost from bone which may decrease the bone density and lead to osteoporosis. Supplementation of estrogen in the form of hormone replacement therapy (HRT) can prevent bone loss, but the therapy can have negative side effects. While HRT is thought to give some protection from colon cancer, osteoporosis, heart disease, macular degeneration, and possibly depression, its negative side effects include increased risk of: stroke or heart attack, blood clots, breast cancer, ovarian cancer, endometrial cancer, gall bladder disease, and possibly dementia. |
SciQ | SciQ-3690 | biochemistry, gas-laws
Title: What is the state of aggregation (gas, liquid) of oxygen in blood? Atmospheric oxygen is in O2 and a gas. Then we inhale the air, our efficient lungs do the magic to filter out the oxygen and push them into the blood stream.
When we say hemo and globin transport the oxygen using the iron ions. In what state oxygen is transported in the blood? as a gas or a liquid or an ion? It is hard for me to conceive of the idea that oxygen would be in gaseous form in the blood. "GAS in blood?" e.g. Arterial Blood Gas Test
Also, how does the lungs convert the gas into something that is compatible to be in blood?
References:
Amount of Oxygen in the Blood Regarding the state of oxygen in blood: It is in solution in the blood plasma (which mostly consists of water), in the form of single molecules. Think of water which you leave exposed to air: carbon dioxide will be captured and dissolved (along with the other gases in air), but these molecules are not gaseous or liquid, but rather "in solution", which is different from the "classical" states.
Back to oxygen: As your reference already states, most of the oxygen in solution will bind to hemoglobin. The actual state of oxygen in that complex has been debated, but it is believed to be reduced by the hemoglobin iron to the superoxide anion, coordinated to Fe$^{3+}$. See Wikipedia on this.
Also, the lungs do not "convert" the atmospheric oxygen to anything, they rather allow, due to their very large surface area, the quick exchange of oxygen/carbon dioxide in solution and in the air.
The following is multiple choice question (with options) to answer.
What blood protein carries oxygen from the lungs to cells throughout the body? | [
"hemoglobin",
"plasma",
"dopamine",
"platelets"
] | A | The blood protein hemoglobin binds with oxygen and carries it from the lungs to cells throughout the body. Heme is a small molecule containing iron that is part of the larger hemoglobin molecule. Oxygen binds to the iron in heme. |
SciQ | SciQ-3691 | observable-universe
Title: What is the rarest stable element in the universe? I am making a hard sci-fi game with a focus on realism, in this game there is a need for a hard element to base money off of. Similar to how gold is used on earth.
I know there are lots of elements that only exist for seconds at a time that are technically rare but wouldn't work as a currency. What element in the universe would aliens be most likely to be trading back and forth? Within our solar system the least abundant, stable and non radioactive element is Tantalum, atomic number 73.
Its chemical inertness,
make it valuable for laboratory and industrial equipment such as reaction vessels and vacuum furnaces
Back in the 1970s and 1980s it was popular to make electronic capacitors using tantalum because they were smaller in size than the electronic capacitors that were made previously. This made them popular for use in hand held calculators and other similar small electronic devices.
Tantalum is dark (blue-gray), dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity. The metal is renowned for its resistance to corrosion by acids.
Element 43, Technetium, is very rare, radioactive and has a short half life. On Earth it is a synthetic material and wouldn't be suitable for your purposes.
Similarly, Promethium, element 61, is rare, but radioactive. The same applies for elements 84 through to 89.
The following is multiple choice question (with options) to answer.
What is the most abundant element in the universe? | [
"hydrogen",
"oxygen",
"helium",
"fluoride"
] | A | Summary By far the most abundant element in the universe is hydrogen. The fusion of hydrogen nuclei to form helium nuclei is the major process that fuels young stars such as the sun. Elements heavier than helium are formed from hydrogen and helium in the interiors of stars. Successive fusion reactions of helium nuclei at higher temperatures create elements with even numbers of protons and neutrons up to magnesium and then up to calcium. Eventually, the elements up to iron-56 and nickel-58 are formed by exchange processes at even higher temperatures. Heavier elements can only be made by a process that involves multiple neutron-capture events, which can occur only during the explosion of a supernova. |
SciQ | SciQ-3692 | N s ) is the product of mass and velocity is measured in and. The speed with which block moves along with the bullet '' any object IIT-JEE Previous Narendra!, are defined in terms of the seven base quantities via a system quantity. In kg and velocity provide step-by-step solutions in as fast as 30 minutes, Showbiz Gaming., N s ) is the product of mass and velocity of 1.5 m/s with a momentum of object... The specification of both a magnitude and direction. negative and anti-clockwise torques are taken positive the specification both! In physics is the product of mass and velocity of an object of mass m moving with a velocity is! Class 09 > Science 1 answers ; Harsh Srivastava 2 years, 8 months ago 2 ; Full... And velocity ) /s the energy possessed by an object of mass and velocity is m\ [ s^ { }... Obtained from these equations and the seven SI base unit for velocity m\. Momentum, and that of velocity is constant, doubts, problems we! Dc Pandey Sunil Batra HC Verma Pradeep Errorless newton 's second law of motion for motion... Any object can do work '' any object that possesses energy can do work vector which! V 1 ) define momentum and it 's SI unit. { -1 } \.... = mass x velocity - it is defined as the ability of an of! 24/7 to provide step-by-step solutions in as fast as 30 minutes it is defined as product of mass and.. * m/s measurements that incorporate time are measured in meter / sec are! Interface Segregation Principle In Agile, 16 Oz Pepsi Glass Bottle, Alkyd Resin Toxicity, Beet And Horseradish Relish, What Is Synthetic Resin Used For, Seattle Sourdough Bread Nutrition Facts, Penguin Definition Slang, Native American Blue Jay Feather Meaning, Bubba Turkey Burger Calories, Rogers County Assessor, " /> (kg*m)/s. For Enquiry. Biology. If a body is moving with velocity, v and having mass, m then momentum of body is p = m × v. SI unit of momentum (p) is kgm s â 1. Write its SI unit. Energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat,
The following is multiple choice question (with options) to answer.
The product of a system’s mass multiplied by its velocity is called what? | [
"linear momentum",
"variation momentum",
"magnetic momentum",
"horizontal momentum"
] | A | 8.1 Linear Momentum and Force Linear Momentum The scientific definition of linear momentum is consistent with most people’s intuitive understanding of momentum: a large, fastmoving object has greater momentum than a smaller, slower object. Linear momentum is defined as the product of a system’s mass multiplied by its velocity. In symbols, linear momentum is expressed as. |
SciQ | SciQ-3693 | evolution, life-history
Title: Has there been any observation of species adapting the evolution process? I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that are only related to the evolution process. Examples could be increase chance of mutations in newborns, change in reproduction age, and similar. I am specifically interested in observation where the evolution process itself has adapted to a change in the environment. Bacteria such as E. coli are known to increase their mutation rate (by switching to a more error prone polymerase among other things) when under stress. This can mean being placed in a medium where it's not adapted to grow (http://www.micab.umn.edu/courses/8002/Rosenberg.pdf) or when treated with antibiotics (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088971/?tool=pmcentrez).
The following is multiple choice question (with options) to answer.
In response to changing environmental conditions, prokaryotic populations can undergo what process in short periods of time? | [
"fusion",
"evolution",
"reproduction",
"extinction"
] | B | |
SciQ | SciQ-3694 | experimental-physics, nuclear-physics, radioactivity, statistics, half-life
$$t_{\rm average} = \frac{6.45\times 10^9\times 365.2422\times 86400}{2.53\times 10^{24}}{\rm seconds} = 8.05\times 10^{-8} {\rm seconds}. $$
So one gets about 12.4 million decays during one second. (Thanks for the factor of 1000 fix.) These decays may be observed on an individual basis. Just to be sure, $T$ was always a lifetime in the text above. The half-life is simply $\ln(2) T$, about 69 percent of the lifetime, because of some simple maths (switching from the base $e$ to the base $2$ and vice versa).
If we observe $\Delta N$ decays, the typical relative statistical error of the number of decays is proportional to $1/(\Delta N)^{1/2}$. So if you want the accuracy "1 part in 1 thousand", you need to observe at least 1 million decays, and so on.
The following is multiple choice question (with options) to answer.
What term means the time in which half of the original number of radioactive nuclei in a sample decay? | [
"quarter-life",
"half-life",
"reduced life",
"partial-life"
] | B | Half-Life Why use a term like half-life rather than lifetime? The answer can be found by examining Figure 31.21, which shows how the number of radioactive nuclei in a sample decreases with time. The time in which half of the original number of nuclei decay is defined as the half-life, t 1 / 2 . Half of the remaining nuclei decay in the next half-life. Further, half of that amount decays in the following half-life. Therefore, the number of radioactive nuclei decreases from. |
SciQ | SciQ-3695 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
What is a shortage of water that causes the soil to dry from the surface down called? | [
"overflowage",
"tidal wave",
"flood",
"drought"
] | D | |
SciQ | SciQ-3696 | zoology, species-identification, entomology
Title: Identification of a segmented black insect in France
Found in the Lot department of southern France. I think this is some sort of soldier fly larva (family Stratiomyidae). That would explain lack of legs. There are thousands of species world wide, with both aquatic and terrestrial larvae, so it might be possible to narrow it down a bit more.
Image from bugguide.net for comparison:
Thanks to @bli for reminding me of dipteran larvae!
The following is multiple choice question (with options) to answer.
What are are segmented invertebrates in phylum annelida called? | [
"flatworms",
"fungi",
"annelids",
"corals"
] | C | Annelids are segmented invertebrates in Phylum Annelida. They include earthworms, polychaete worms, and leeches. Annelids have a coelom and several organ systems. Their body segments may have a variety of different structures such as tentacles or suckers. Annelids may be predators, parasites, filter feeders, or decomposers. |
SciQ | SciQ-3697 | brain
Title: When a thought 'crosses your mind', does it literally cross between left and right cerebral hemispheres? I've heard that part of cognitive processing is information passing between left and right cerebral hemispheres.
This is what happens in the Cerebral Cortex which is divided into two hemispheres,
left brain and right brain connected by a thick layer of nerve fibers called the corpus callosum. These nerve fibers allow messages to pass between the left and right brain
hemispheres
My question is When a thought 'crosses your mind', does it literally cross between left and right cerebral hemispheres?
Assumptions:
I'm making a big leap from 'electronic impulses of neurons' to 'thoughts'. Neuroscience doesn't really have a clear model for what a "thought" consists of exactly. Certain processes that are involved in thought have begun to be mapped--for example, this recent paper talks about a model for how the brain associates location in space with it's own mental map (http://www.ncbi.nlm.nih.gov/pubmed/24462102, I'll try to find something related that's not behind a paywall...). This one doesn't address your particular problem though, they only measured activity on one side of the brain. So basically, it might be possible to partially answer your question for more specific brain processes, but different kinds of "thoughts" are processed in different ways.
And of course I am also conflating impulses crossing the corpus callosum with the thoughts themselves, but I don't think this is really accurate. The most popular models in the labs I'm familiar with suggest that a "thought" is composed of a bunch of neural activity taken together rather than the activities of a few neurons on their own. But that might ultimately just be arguing semantics.
The following is multiple choice question (with options) to answer.
What is the connection between the two hemispheres of the brain called? | [
"spinal cord",
"cranial septum",
"cerebral cortex",
"corpus callosum"
] | D | Left Brain, Right Brain Popular media often refer to right-brained and left-brained people, as if the brain were two independent halves that work differently for different people. This is a popular misinterpretation of an important neurological phenomenon. As an extreme measure to deal with a debilitating condition, the corpus callosum may be sectioned to overcome intractable epilepsy. When the connections between the two cerebral hemispheres are cut, interesting effects can be observed. If a person with an intact corpus callosum is asked to put their hands in their pockets and describe what is there on the basis of what their hands feel, they might say that they have keys in their right pocket and loose change in the left. They may even be able to count the coins in their pocket and say if they can afford to buy a candy bar from the vending machine. If a person with a sectioned corpus callosum is given the same instructions, they will do something quite peculiar. They will only put their right hand in their pocket and say they have keys there. They will not even move their left hand, much less report that there is loose change in the left pocket. The reason for this is that the language functions of the cerebral cortex are localized to the left hemisphere in 95 percent of the population. Additionally, the left hemisphere is connected to the right side of the body through the corticospinal tract and the ascending tracts of the spinal cord. Motor commands from the precentral gyrus control the opposite side of the body, whereas sensory information processed by the postcentral gyrus is received from the opposite side of the body. For a verbal command to initiate movement of the right arm and hand, the left side of the brain needs to be connected by the corpus callosum. Language is processed in the left side of the brain and directly influences the left brain and right arm motor functions, but is sent to influence the right brain and left arm motor functions through the corpus callosum. Likewise, the left-handed sensory perception of what is in the left pocket travels across the corpus callosum from the right brain, so no verbal report on those contents would be possible if the hand happened to be in the pocket. |
SciQ | SciQ-3698 | terminology, oscillators, vibrations
This was added after the question has already been marked as answered
I've been doing some more research and I would like to add a collection of interesting resources. Maybe it will help someone out in the future:
"Drum Head vibrations" (snaresience.com): http://www.snarescience.com/articles/drum-head-vibration.php – Contains slow motion footage of a membrane being excited by a loudspeaker. You can easily see the standing waves and respective nodes. The term mode is heavily used in physics and for this reason its usage tends to be not very stringent. It generally refers to the 'natural' motions of oscillating systems.
Let's get a feel for it: Take any system with an oscillating motion, be it a stringed instrument, drums, pendulums, radio antennas, etc. Jiggle or kick one of these and see how they react, i.e. pick a string and listen how it reacts. Looking at this closely, one can actually tell apart these reactions into a set of motions that happen at once and are added together to give the reaction. Each of these motions happens at a well defined frequency and is called a mode.
If you pick a string it will oscillate in many of its modes and you hear all their frequencies mixed together. Pick a string in a different position or hit a drum at a different point and notice that it changes its sound. This means that the relative strength of the modes was changed. For example a string picked at its midpoint sounds like a harp and picked closer to its end sounds like guitar.
With this control one can try to pick/jiggle/kick the system in a way to single out one mode only. This is what happens with Chladni figures on metal plates with sand. Similarly, humming next to a string to make it vibrate, singles out the mode matching the humming frequency.
Talking about modes: In the end, your oscillator has a set of modes and each mode is directly related to a frequency, which is the speed at which these motions naturally happen. The term mode is used to refer to the pattern of motion as well as to the frequency. So saying
The following is multiple choice question (with options) to answer.
Banging on a drum is an example of which type of energy? | [
"solar.",
"potential",
"mechanical",
"molecular"
] | C | |
SciQ | SciQ-3699 | microbiology
Title: How exactly are petri dishes used (e.g. in medicine)? I know that petri dishes with a growth medium are used to grow micro organisms. I guess this works as follows:
The petri dish has to be kept sterile. To make it easier, I guess one could cool it.
The microorganisms are somehow put on the petri dish.
The petri dish is put in an incubator (e.g. 37 °C if one wants to simulate the human body).
After some time (how long?) one can look at the colonies.
Does one only look at them with the naked eye or is there a way to make more detailed studies?
For example, when I have an illness, can the doctor (for some illnesses) simply use this petri dish / naked eye technique to confirm a hypothesis what kind of illness I have? I think the petri dishes you are referring to are also called agar plates. Agar is a 'growth medium' for microorganisms. It provides the nutrients that the microorganisms need to survive. It can also contain main other 'things', such as antibiotics or pH color change indicators. There are many types of agar, for example, tryptic soy agar is used to grow E. coli. I think the oven you are referring to is called an incubator. Incubators provide the atmosphere, particularly temperature, needed for the organisms to grow. There are many types of incubators. Some microorganisms actually cannot grow in oxygen rich environments, and some only grow at specific temperatures. These organisms must be incubated under their preferred conditions in order for them to grow.
And yes, a lot can be learned from simply looking at the agar with the organisms on it. What exactly can be learned depends on the growth medium (agar or other medium).
To summarize, petri-dishes are just the plastic dishes that contain growth medium. And incubators are usually refrigerator looking things that provide the proper temperature for the organisms to grow. The goal is generally to mimic the natural environment of the organism, but as I stated, scientists often add many other things to the environment for experimental and diagnostic purposes.
Here is a list of common agars used in bacteriology http://learn.chm.msu.edu/vibl/content/differential/
The following is multiple choice question (with options) to answer.
What do microbes use to make food? | [
"chemicals",
"sunlight",
"plants",
"nitrogen"
] | A | Microbes use chemicals to make food. The chemicals pour out of a crack on the ocean floor at a mid-ocean ridge. What consumers live in this ecosystem?. |
SciQ | SciQ-3700 | telescope, space-telescope
Space based telescopes still hold a significant edge in parts of the spectrum blocked by the atmosphere such as UV and IR (Webb), and for certain tasks involving long-term high accuracy photometry (Kepler) and astrometry (Gaia). But for general purpose use, the balance seems firmly on the ground's side for large telescopes.
This will change if space flight becomes cheaper -- the SpaceX BFR, for example, with its 9 meter fairing and dramatically lower launch costs, offers great hope for space telescopes.
The following is multiple choice question (with options) to answer.
Space telescopes avoid such problems completely since they orbit outside the what? | [
"atmosphere",
"galaxy",
"earth's crust",
"ozone layer"
] | A | Telescopes on Earth all have one big problem: Incoming light must pass through the atmosphere. This blocks some wavelengths of radiation. Also, motion in the atmosphere distorts light. You see this when you see stars twinkling in the night sky. Many observatories are built on high mountains. There is less air above the telescope, so there is less interference from the atmosphere. Space telescopes avoid such problems completely since they orbit outside the atmosphere. |
SciQ | SciQ-3701 | human-anatomy
Atraumatic dislocation.
This occurs when the shoulder dislocates with minimal force such as reaching up for an object or turning over in bed. Usually it will 'pop' back in itself or with a little help. Normally this type of dislocation does not need reducing in A&E. It can occur regularly throughout the day and will be associated with certain positions the arm is placed into. This type of dislocation is associated with people that have 'lax' joints, for example people who hyper-extend their knees and elbows and can get the palms of both hands onto the floor with ease. This joint laxity is normal for these people and the onset of dislocation can be associated with a change in how the muscles around the shoulder are interacting with each other or a change in posture/ position of the arm. This can produce an imbalance in the control of the joint. Referral for appropriate physiotherapy is the initial form of management. The physiotherapist should look at the way in which the muscles and shoulder joint is moving and posture aiming to restore the balance. Treatment can 'cure' the problem as long as the exercises and advice is continued, but in some cases there is only minimal or nil benefit. At this point surgical intervention is indicated.
Positional Non-traumatic dislocations.
This group of people can dislocate their shoulders without any form or history of trauma. Some may have started out dislocating their shoulder as a party trick; others may have always had shoulders that just 'fall' out of joint. This type of dislocation is usually painless and can be put back in easily. Both shoulders are typically involved. The cause of this type of dislocation is usually a result of what we call 'abnormal muscle patterning' which means the strong muscles around the shoulder joint are not working in the correct order causing them to pull the shoulder out of joint with active movement in the particular direction such as lifting the arm forward above the head or out to the side and above the head. The main treatment for this is physiotherapy that looks at re-sequencing the muscles in order to prevent further dislocations. Occasionaly surgery in the form of thermal capsular shrinkage or plication may be neccessary.
The following is multiple choice question (with options) to answer.
Tendons connecting the scapula to the humerus form what, which is the circle of tendons around the shoulder joint? | [
"knee cuff",
"wrist cuff",
"rotator cuff",
"thigh cuff"
] | C | The rest of the shoulder muscles originate on the scapula. The anatomical and ligamental structure of the shoulder joint and the arrangements of the muscles covering it, allows the arm to carry out different types of movements. The deltoid, the thick muscle that creates the rounded lines of the shoulder is the major abductor of the arm, but it also facilitates flexing and medial rotation, as well as extension and lateral rotation. The subscapularis originates on the anterior scapula and medially rotates the arm. Named for their locations, the supraspinatus (superior to the spine of the scapula) and the infraspinatus (inferior to the spine of the scapula) abduct the arm, and laterally rotate the arm, respectively. The thick and flat teres major is inferior to the teres minor and extends the arm, and assists in adduction and medial rotation of it. The long teres minor laterally rotates and extends the arm. Finally, the coracobrachialis flexes and adducts the arm. The tendons of the deep subscapularis, supraspinatus, infraspinatus, and teres minor connect the scapula to the humerus, forming the rotator cuff (musculotendinous cuff), the circle of tendons around the shoulder joint. When baseball pitchers undergo shoulder surgery it is usually on the rotator cuff, which becomes pinched and inflamed, and may tear away from the bone due to the repetitive motion of bring the arm overhead to throw a fast pitch. |
SciQ | SciQ-3702 | statistical-mechanics, probability
Title: Probability of finding n particles in a volume v I'm trying to calculate the probability of finding $n$ particles in a certain volume $v$ in a system with a total of $N$ particles and total volume of $V$. My problem is that I've tried two approaches which both seem valid to me, but give differing answers.
One approach is to use binomial probability, where the probability of success (particle in the volume of interest) is $\frac{v}{V}$. Furthermore, the particles are indistinguishable, so it doesn't matter the order of "successes" and "failures". This gives:
$P=(1-\frac{v}{V})^{N-n}\,(\frac{v}{V})^{n}\,\frac{N!}{(N-n)!n!}$
My other approach is to say to start saying that any configuration (remembering particles are indistinguishable) has equal probability and so the probability for our event is simply $P=\frac{\mathrm{\#\ of\ configurations\ with\ n\ particles\ in\ the\ cell}}{\mathrm{\#\ of\ configurations}}$. Now from combinatorics, the number of configurations is $\binom{N+\frac{V}{v}-1}{N}$, and the number of configurations with $n$ particles in $v$ is $\binom{N-n+\frac{V}{v}-2}{N-n}$. This gives a probability:
The following is multiple choice question (with options) to answer.
The number of particles of a substance in a given volume is known as? | [
"concentration",
"frequency",
"mass",
"range"
] | A | Concentration is the number of particles of a substance in a given volume. When the concentration of reactants is higher, the reaction rate is faster. At higher concentrations, particles of reactants are crowded closer together, so they are more likely to collide and react. Did you ever see a sign like the one in Figure below ? You might see it where someone is using a tank of pure oxygen for a breathing problem. The greater concentration of oxygen in the air makes combustion rapid if a fire starts burning. |
SciQ | SciQ-3703 | electrostatics, electricity, electric-current, charge, flow
Title: Why does the flow of charge even create electricity? Okay this is a question I’ve asked a lot of places but I always get its the flow of charges and it’s like a property. What I don’t really understand is how is this flow of charges creating electric current.
My guess is that as these charges get closer to the desired potential(to satisfy potential difference) Energy is released which happens continuously and it is the reason for electric current atleast in a conductor.
Can I get some insight into what is happening down at the quantum level. First of all you have to understand that flow of electrical current and dissipation of energy are two completely different concepts.
Electrical current: The flow of electrical charges is called electrical current. This is like a definition and has nothing to do with dissipation. There are systems, where current flows without dissipation. At the elementary level, you get the electrical current $I$, if you count, how many elementary charges $e$ cross a specific cross-sectional area of your "conductor" per second. Mathematically this means:
$$ I := \frac{e\Delta N}{\Delta t},$$
where $I$ is the current, $\Delta t$ is the time interval (e.g. 1 second), $e$ is the elementary charge, and $\Delta N$ is the number of elementary charges that you count within time $\Delta t$.
Usually, conductors are metals, and you may think of the cross sectional area of a copper wire, for example. But you can also imagine other "conductors" that are liquids with ions in them, or even gases with charged atoms in them.
Electrical resistance: Flowing charge carriers dissipate energy, if they scatter with other particles and thereby lose energy. In metals, for example, electrons forming the electrical current will scatter from lattice vibrations (phonons) and thereby dissipate energy. This energy dissipation leads to electrical resistance, usually denoted by $R$.
The following is multiple choice question (with options) to answer.
Potential differences from various voltage sources are necessary in order to create electrical fields, which result in what flow of charge? | [
"output",
"voltage",
"current",
"wattage"
] | C | 20.2 Ohm’s Law: Resistance and Simple Circuits What drives current? We can think of various devices—such as batteries, generators, wall outlets, and so on—which are necessary to maintain a current. All such devices create a potential difference and are loosely referred to as voltage sources. When a voltage source is connected to a conductor, it applies a potential difference V that creates an electric field. The electric field in turn exerts force on charges, causing current. |
SciQ | SciQ-3704 | meteorology, atmosphere, wind, air-currents
Title: Where does wind come from? Wind is (according to Wikipedia) the flow of gases on a large scale.On the surface of the Earth, wind consists of the bulk movement of air.
What forces would cause such a mass movement of air? Wind is caused by pressure differences. Think of a balloon full of air; poke a hole in it and the air comes out. Why? Because the pressure in the balloon is higher than outside, and so to regain equal pressure, mass moves and that is the wind.
There is a bit more to this in the atmosphere as the Earth rotates and near the surface friction also plays a role. The equation of motion is the Navier-Stokes and in vector form in Cartesian space is:
$$\dfrac{\partial\mathbf u}{\partial t} = - \mathbf u \cdot \nabla \mathbf u -\dfrac{1}{\rho}\nabla p-2 \mathbf \Omega \times \mathbf u + \mathbf g + \mathbf F$$
In this equation, $\mathbf u$ is the vector wind, $(\mathbf u \cdot \nabla)$ is the advection operator, $\rho$ is density, $\mathbf \Omega$ is the vector rotation of the Earth, $\mathbf g$ is effective gravity and $\mathbf F$ is friction.
The LHS is the time rate of change of the wind at a point in space (as opposed to following the parcel). The RHS represent a number of factors that produce a change in the wind. From left to right:
Advection of momentum (non-linear)
Pressure gradient force (this is wind blowing from high to low pressure)
Coriolis force (this turns wind to the right in the NH and left in the SH and causes the wind to flow parallel to isobars)
gravity (provides hydrostatic balance with the PGF in the vertical)
Friction (in the boundary layer you may see this as $\nu\nabla^2\mathbf u$)
The following is multiple choice question (with options) to answer.
What effect is caused by air moving over the earth's surface as it spins? | [
"dopple effect",
"coriolis effect",
"pruett effect",
"mazinho effect"
] | B | Earth is spinning as air moves over its surface. This causes the Coriolis effect. Winds blow on a diagonal over the surface, instead of due north or south. From which direction do the northern trade winds blow?. |
SciQ | SciQ-3705 | acid-base, analytical-chemistry, experimental-chemistry, extraction
Title: Separation of Binary mixture? I will be given a binary mixture containing two unknown compounds(the mixture could be either liquid or solid- I don't know yet). The plan of the experiment is to identify the two compounds. So my primary concern is to separate the binary mixture and purify the individual compounds(then the subsequent classification tests/NMR/IR analysis should be straightforward). I am thinking of doing an acid-base extraction but don't know how to since I don't know any physical properties of the compounds. Any suggestions would be appreciated. N.B.: the advice below mostly applies to organic compounds. If you're dealing with inorganic salts, or solutions thereof, the approach will be very different.
For a solid mixture, I would take an IR first. That should allow you to rule out potentially useless chemical tests by identifying the functional groups present in your mixture without wasting any of the sample. This would also give you some indication whether acid/base extraction is likely to be of any use. After that, it seems logical to test solubility in a wide range of solvents and at different temperatures. If you can find one that dissolves your mixture only partially at low temperature, but completely at high temperature, then you can likely separate the components immediately by recrystallization. Judicious use of a centrifuge can help if the crystals form a fine suspension.
In the case of a liquid mixture, I would again take an IR initially. In some cases, one component of the mixture can be chemically separated, and IR results would again be useful in determining the viability of that approach. Ketones and aldehydes, for example, will react to form semicarbazones that can be recrystallized and then identified by melting point. As far as physical methods of separation, standard are distillation and fractional freezing.
The following is multiple choice question (with options) to answer.
The separation of compounds on the basis of their solubilities in a given solvent is known as what? | [
"separate crystallization",
"simplest crystallization",
"fractional crystallization",
"nuclei crystallization"
] | C | Solubility may increase or decrease with temperature; the magnitude of this temperature dependence varies widely among compounds. Notice in particular the curves for NH4NO3 and CaCl2. The dissolution of ammonium nitrate in water is endothermic (ΔHsoln = +25.7 kJ/mol), whereas the dissolution of calcium chloride is exothermic (ΔHsoln = −68.2 kJ/mol), yet Figure 13.9 "Solubilities of Several Inorganic and Organic Solids in Water as a Function of Temperature" shows that the solubility of both compounds increases sharply with increasing temperature. In fact, the magnitudes of the changes in both enthalpy and entropy for dissolution are temperature dependent. Because the solubility of a compound is ultimately determined by relatively small differences between large numbers, there is generally no good way to predict how the solubility will vary with temperature. The variation of solubility with temperature has been measured for a wide range of compounds, and the results are published in many standard reference books. Chemists are often able to use this information to separate the components of a mixture byfractional crystallization, the separation of compounds on the basis of their solubilities in a given solvent. For example, if we have a mixture of 150 g of sodium acetate (CH3CO2Na) and 50 g of KBr, we can separate the two compounds by dissolving the mixture in 100 g of water at 80°C and then cooling the solution slowly to 0°C. According to the temperature curves in Figure 13.9 "Solubilities of Several Inorganic and Organic Solids in Water as a Function of Temperature", both compounds dissolve in water at 80°C, and all 50 g of KBr remains in solution at 0°C. Only about 36 g of CH3CO2Na are soluble in 100 g of water at 0°C, however, so approximately 114 g (150 g − 36 g) of Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-3706 | meteorology, atmosphere, wind, air-currents
Title: Where does wind come from? Wind is (according to Wikipedia) the flow of gases on a large scale.On the surface of the Earth, wind consists of the bulk movement of air.
What forces would cause such a mass movement of air? Wind is caused by pressure differences. Think of a balloon full of air; poke a hole in it and the air comes out. Why? Because the pressure in the balloon is higher than outside, and so to regain equal pressure, mass moves and that is the wind.
There is a bit more to this in the atmosphere as the Earth rotates and near the surface friction also plays a role. The equation of motion is the Navier-Stokes and in vector form in Cartesian space is:
$$\dfrac{\partial\mathbf u}{\partial t} = - \mathbf u \cdot \nabla \mathbf u -\dfrac{1}{\rho}\nabla p-2 \mathbf \Omega \times \mathbf u + \mathbf g + \mathbf F$$
In this equation, $\mathbf u$ is the vector wind, $(\mathbf u \cdot \nabla)$ is the advection operator, $\rho$ is density, $\mathbf \Omega$ is the vector rotation of the Earth, $\mathbf g$ is effective gravity and $\mathbf F$ is friction.
The LHS is the time rate of change of the wind at a point in space (as opposed to following the parcel). The RHS represent a number of factors that produce a change in the wind. From left to right:
Advection of momentum (non-linear)
Pressure gradient force (this is wind blowing from high to low pressure)
Coriolis force (this turns wind to the right in the NH and left in the SH and causes the wind to flow parallel to isobars)
gravity (provides hydrostatic balance with the PGF in the vertical)
Friction (in the boundary layer you may see this as $\nu\nabla^2\mathbf u$)
The following is multiple choice question (with options) to answer.
What is the process by which wind blows to make the ground surface gets lower and rockier ? | [
"layering",
"stagnation",
"deflation",
"inflation"
] | C | Wind blows small particles away. As a result, the ground surface gets lower and rockier; this is called deflation . The rocks that are left are called desert pavement . Desert pavement is a surface covered by gravel-sized particles that are not easily moved by wind. |
SciQ | SciQ-3707 | atmosphere, carbon-cycle
Title: For a tree over its entire existence, does it actually have a net negative effect on atmospheric CO2? A tree while alive converts CO2 + water -> carbohydrates + O2. However, once the tree dies, it decays, releasing CO2 back into the atmosphere. My question is, over an individual tree's overall existence, does a tree actually contribute to a reduction in atmospheric CO2?
I'm aware there's other pathways a tree could end up as a more long term carbon store (carbonaceous rocks), but mostly interested in if a tree were to die and fall in a forest, decay in 50-150 years, would it have contributed to a net reduction in CO2, or does a tree typically act as more of a temporary 100+ year store of CO2? A brief review of recent non-paywalled available literature indicates that such an effect likely exists but that it is difficult to quantify based on currently available data.
Some amount of carbon from trees can be sequestered in the soil for periods time significantly longer than the typical above-ground decomposition time of organic matter, potentially for millennia. This clearly lengthens the carbon cycle time, but it is not clear to me whether this represents carbon storage, as there does not seem to be a well established minimum cut-off time for this. The primary source for soil-sequestered carbon are tree roots, with leaf litter constituting a secondary source.
The following paper (preprint online) addresses the question in the specific context of agroforestry, i.e. cropland interspersed with trees. The paper notes multiple times that the processes involved in soil sequestration are not well understood and that quantitative measurements and estimates vary widely, as one would expect based on differences in climatic and soil condition. Note on units: A Mg corresponds to a metric ton.
Klaus Lorenz and Rattan Lala, "Soil organic carbon sequestration in agroforestry systems. A review." Agronomy for Sustainable Development, Vol. 34, No. 2, April 2014, pp. 443-454.
The following is multiple choice question (with options) to answer.
Because trees add water vapor to air, cutting down forests leads to longer periods of what? | [
"flooding",
"ice",
"drought",
"harvest"
] | C | Water shortages are common in much of the world. People are most likely to run short of water during droughts. A drought is a period of unusually low rainfall. Human actions have increased how often droughts occur. One way people can help to bring on drought is by cutting down trees. Trees add a lot of water vapor to the air. With fewer trees, the air is drier and droughts are more common. |
SciQ | SciQ-3708 | species-identification, zoology, marine-biology, invertebrates
Title: Help with jellyfish species identification Our research group (Evolutionary Genetics Group, University of Zurich) has received a letter from a special needs child who has kindly asked us to identify three jellyfish species.
Unfortunately, the letter does not include anything else except three rather low quality cutouts from what I assume is a childrens book. Nobody in our lab has any knowledge about jellyfish taxonomy so any help is greatly appreciated. Be warned that these are just best guesses - as you said yourself, these aren't great images for identification as they appear to be simple drawings:
1) this looks a lot like Aurelia aurita - though the lack of any internal patterning in the drawing makes me think perhaps otherwise.
image source: https://www.leisurepro.com/blog/wp-content/uploads/2017/05/shutterstock_272438348.jpg, https://holidays-majorca.co.uk/wp-content/uploads/2017/01/Aurelia-Aurita-S-300x225.jpg
2) possibly a Turritopsis dohrnii or nutricala - if so then this is the 'immortal' jellyfish. shape of bell is correct and the lappets seem reasonably close, it's just the internal structures that I'm not sure about.
image source: https://www.cairnsholidayspecialists.com.au/shared_resources/media/irukandji-jellyfish-in-far-north-18836_400x322.jpg
3) Very unsure about this one, but potentially a Atolla wyvillei? definitely has some visual features in common and I can't find anything else that's similar. I can also see how an artist would derive that image from this species.
The following is multiple choice question (with options) to answer.
Some sea anemones establish what kind of relationship with hermit crabs by attaching to the crab’s shell? | [
"predatory",
"parasitic",
"pathogenic",
"mutualistic"
] | D | The mouth of a sea anemone is surrounded by tentacles that bear cnidocytes. The slit-like mouth opening and pharynx are lined by a groove called a siphonophore. The pharynx is the muscular part of the digestive system that serves to ingest as well as egest food, and may extend for up to two-thirds the length of the body before opening into the gastrovascular cavity. This cavity is divided into several chambers by longitudinal septa called mesenteries. Each mesentery consists of one ectodermal and one endodermal cell layer with the mesoglea sandwiched in between. Mesenteries do not divide the gastrovascular cavity completely, and the smaller cavities coalesce at the pharyngeal opening. The adaptive benefit of the mesenteries appears to be an increase in surface area for absorption of nutrients and gas exchange. Sea anemones feed on small fish and shrimp, usually by immobilizing their prey using the cnidocytes. Some sea anemones establish a mutualistic relationship with hermit crabs by attaching to the crab’s shell. In this relationship, the anemone gets food particles from prey caught by the crab, and the crab is protected from the predators by the stinging cells of the anemone. Anemone fish, or clownfish, are able to live in the anemone since they are immune to the toxins contained within the nematocysts. Anthozoans remain polypoid throughout their lives and can reproduce asexually by budding or fragmentation, or sexually by producing gametes. Both gametes are produced by the polyp, which can fuse to give rise to a free-swimming planula larva. The larva settles on a suitable substratum and develops into a sessile polyp. |
SciQ | SciQ-3709 | prokaryotes
Title: Are chromosomal and plasmid DNA in the nucleoid? I know plasmid DNA is not part of the chromosome, according to my textbook, but can you still class it as being part of the nucleoid?
Also is chromosomal DNA in the nucleoid? "Nucleoid" (literally means nucleus-like), is a quite old term for "bacterial chromosome" (Better to write prokaryotic chromosome since in both type of prokaryotes i.e. Archaea (former archaebacteria) and bacteria (former eubacteria) the structure is similar).
Nucleoid structurally normally excludes the plasmid-DNA (the plasmid DNA is like additional or accessory). However sometimes a plasmid DNA could go through recombination with prokaryotic chromosome 's DNA (As seen in Hfr strain of Escherichia coli)
"Chromosome" in very brief means a structure made of DNA + Protein. In case of "bacterial-chromosome", it contains both DNA and Protein; and if you take away the protein from bacterial chromosome; what you get, is the chromosomal DNA.
Reference:
Microbiology / Pelczar, Chan and Noel/ Edition-5;
Part 2: Bactria,
Chapter 5 (Morphology and fine structure of bacteria)
"Because it is not discrete nucleus, this nebulous structure has been designated by such terms as the nucleoid , the chromatin body, the nuclear equivalent, even the bacterial chromosome"
General Microbiology / Hans G. Schlegel / Edition-7:
Chapter-2 ; The cell and its structure:
2.2 The prokaryotic cell (protocyte) -> 2.2.1: The bacterial 'nucleus'
" Plasmids : In addition to chromosomal DNA, many bacteria contain extrachromosomal DNA in closed, circular, double stranded form. These autonomously replicating DNA elements are called plasmids. Linear plasmids have been found in some bacteria"
The following is multiple choice question (with options) to answer.
Prokaryotic cells do not have a nucleus but instead generally have a single chromosome, a piece of double-stranded dna located in an area of the cell called the what? | [
"cytoplasm",
"lysosome",
"nucleoid",
"spicule"
] | C | The Prokaryotic Cell Recall that prokaryotes (Figure 22.10) are unicellular organisms that lack organelles or other internal membrane-bound structures. Therefore, they do not have a nucleus but instead generally have a single chromosome—a piece of circular, double-stranded DNA located in an area of the cell called the nucleoid. Most prokaryotes have a cell wall outside the plasma membrane. |
SciQ | SciQ-3710 | fluid-dynamics, pressure, drag
Title: What is the resistance of an object travelling through static fluid at different pressures? I'm interested in the resistance a body feels as it travels through a static fluid in a tube (of a fixed radius), at different pressures.
I would assume that as the pressure is reduced, the resistance will also be decreased. Does this relate to the Drag Force equation, or is there a better explanation, such as Bernoulli? As mentioned in one of the comments, if the fluid is incompressible (i.e. - has constant density) then the absolute level of the pressure will not affect the drag.
However if the fluid is a gas, then the pressure and density will be strongly related (directly proportional for ideal gases). And the density of the fluid enters into the equation for the dynamic pressure, so it does affect the drag.
For a constant drag coefficient, the drag will be directly proportional to the density, so for streamlined shapes at sufficiently large Reynolds' numbers, the drag will be approximately proportional to the pressure.
This should be true even if the Mach number of the flow is small enough for the incompressible flow equations to be used.
The following is multiple choice question (with options) to answer.
What measures a fluid’s resistance to flow? | [
"surface tension",
"density",
"viscosity",
"elasticity"
] | C | Viscosity measures a fluid’s resistance to flow – the higher the viscosity, the slower the flow of the material. One factor that affects viscosity is the strength of the intermolecular forces in the material. Molecules that exhibit higher intermolecular forces tend to have higher viscosities. Temperature also influences viscosity. A higher temperature results in a decrease in viscosity, since molecules are moving faster and the intermolecular forces are more easily disrupted. Most cooking oils are more viscous than water, but when heated, the viscosity decreases and the oil spreads more easily. Motor oils are ranked by viscosity. Lower viscosity oils provide less drag on the engine, but they are also used up faster than a higher-viscosity material. |
SciQ | SciQ-3711 | homework-and-exercises, electric-circuits, electric-current
Title: Current and misplaced switch I know this is a very noob question, but i just can't help it. Anyways,here is pretty simple circuit
Now after the circuit is changed this way, why is the current going to be infinitely high??
I hope the question is clear. I am no expert but I will try to give you reason for your question..
As Ohm's law states that the current $I$ through a conductor between two points is directly proportional to the voltage $V$ across the two points with proportionality constant, resistance $R$
Source : Wikipedia
i.e
$$I =\frac{V}{R}$$
in which if voltage $V$ is constant, current $I$ will be inversely proportional to resistance $R$ so if resistance decreases, current will increase i.e
$$I \propto \frac{1}{R}$$
So in your first diagram, putting value in equation we get :
$$50.10^{-3} =\frac{6}{R} => R = 120 \Omega$$
And in your second diagram, when switch is closed circuit will be shorted so circuit resistance $R$ will approach $0$ (R~0)
$$I =\frac{6}{0} $$
Current $I$ will approch Infinite ($I$ ~ undefined)
The following is multiple choice question (with options) to answer.
What happens to the wire in a fuse if it's current rating is exceed? | [
"disappears",
"it melts",
"sparks",
"ignites"
] | B | The image above is one type of electrical fuse. This fuse has a specially designed wire inside glass housing. The wire inside the glass is made of a particular metal and with a particular thickness to give the wire an exact resistance. This resistance will allow passage of normal current plus a marginal percentage more. If, however, the current exceeds the allowed value, the wire in the fuse will heat and melt, thus interrupting current flow through the circuit. The fuse wire is placed in the glass housing and a fuse mount to insulate the melting wire from its surroundings. Any unintended increase in current, such as short circuits, overloading, mismatched loads, or device failure will cause the fuse to burn out – protecting the other parts of the circuit from overheating and further damage. |
SciQ | SciQ-3712 | climate, seasons, ice-age, axial-obliquity
Image originally from The Petroleum System Blog
Using that formula, the temperature at the poles (reduced to sea level) would be -16.8 °C (from the figure actual data points it can be seen that in real life the south pole is much colder than the north pole).
Now, the previous assumptions contradicts the requirement of "equilibrium", because the above scenario is far from steady state.
So now I will go on to try to describe what would happen to Earth's climate in your hypothetical scenario:
One thing that we learned by studying how the Milankovitch cycles trigger and reverse Pleistocene ice ages, is that to initiate an ice age cold winters are not necessary, what is needed are cold or mild summers.
Currently, the inclination of Earth axis (a.k.a. obliquity) varies between 22° and 24.5° , with a mean period of 41,040 years. When the inclination is 22°, mild summers occur and, therefore, the perfect condition to initiate an ice age (specially when combined with other ad-hoc orbital conditions). The permanent equinox situation you propose, is equivalent to an obliquity of 0°, that would lead to the coldest possible summer (this is, no summer at all). Therefore, such condition would set the Earth on track for an intense and never-ending ice age.
Let me explain how this could work: Using the formula above, the temperatures would be permanently below zero between the poles and latitudes 58.3°. Therefore, snow would start to accumulate in those areas, building an ice sheet and once the ice sheet gets thick enough it would start flowing outwards.
Figure from Lumen Learning.
The ice sheet then becomes self-sustaining due to two positive feedbacks:
Due to its high albedo, it would reflect most of the solar radiation back to the space, cooling down the Earth.
As the ice sheet advance, its thickness adds to the elevation of the terrain, therefore the surface is higher and colder, allowing snowfall beyond the 58.3° of latitude. The thicker it grows the more it can advance towards the equator.
The following is multiple choice question (with options) to answer.
Polar climates include polar and which other kind of tundra? | [
"tropic",
"mountains",
"arid",
"alpine"
] | D | Polar climates include polar and alpine tundra. Polar Tundra in Northern Alaska (70° N latitude), Alpine Tundra in the Colorado Rockies (40° N latitude). |
SciQ | SciQ-3713 | genetics, homework, human-genetics
Title: What are sex linked traits? Which of the two definitions of sex-linked trait is correct?
Traits controlled by genes present on the non-homologous region of sex chromosomes are called sex-linked traits.
Bodily traits controlled by genes present on the non-homologous regions of sex chromosomes are called sex-linked traits. Here by bodily traits I mean traits that are not involved with sex of an organism.
I read the first definition in the book Competition Science Visionand also from Instant notes genetics (page 163).
The following is an excerpt from the latter
Sex linkage is not displayed by genes which map to a small segment of X chromosome, the pseudoautosomal region, the part of X chromosome that pairs with Y chromosome in meiosis.
The second definition is made up but sounds potentially intuitive to me. The first definition is correct.
A sex-linked trait is a trait affected by a locus on a sex chromosome.
If you google sex-linked trait, you will find this same definition (not the exact same words) over and over again.
The definition of sex-linked trait is NOT restricted to traits that are not unrelated to primary or secondary sexual organs. Any phenotypic trait can be sex-linked as long as the causal locus is on a sexual chromosome.
The following is multiple choice question (with options) to answer.
What disease is given as an example of a sex-linked trait? | [
"emphysema",
"hypertension",
"hemophilia",
"arthritis"
] | C | Hemophilia is a sex-linked trait. Carrier mothers can pass along the affected allele to 50% of their sons. Females with hemophilia would have to receive an affected allele from each parent, making females with hemophilia rare. |
SciQ | SciQ-3714 | food, decomposition
Title: Worm compost cannot have cooked food I live in the Netherlands and it is getting fashionable to compost with worms. After investigating a few websites I noticed that most websites suggested that I cannot feed the worms leftovers from citrus fruits. This seems logical. I then started noticing that people advise against feeding the worms cooked food.
I'm no biologist but I cannot imagine a reason why cooked food is bad for the worms. Could anybody explain why this might be in layman’s terms? There are a few reasons for not feeding cooked foods to worms (Eisenia spp.) in a smaller household size worm farm. It's not because the food is cooked but what it often contains.
The earthworm used in vermiculture is usually Eisenia fetida (red wigglers) though other Eisenia species are sometimes used. All Eisenia are epigeic species meaning they live in the junction of decomposing organic matter (such as leaf litter, aging manure, rotted fallen trees) and their natural food is decaying plant matter and bacteria that are also digesting the organic matter. They don't make use of small dead animals (meat and fat).
In large scale commercial vermiculture operations, leftover and past-due-date foods from restaurants, institutions, nursing homes and schools are used along with plant matter and carboard and paper. I'm not sure how they balance cooked foods but possibly much less is used than plant matter.
The fact food is cooked isn't the problem but what's in it and/or what happens to it when added to the bin. If you have leftover vegetables and fruit that's been cooked with no added salt, it's perfectly acceptable. A certain amount of sweetened cooked fruit is also fine as the worms will eat that too. But ready-made foods usually have preservatives, salt, fats and spices added. Either worms won't eat it, leading to odour caused by mouldy rotten food, or it can make them unthrifty and even killing off your worms if it's fed them repeatedly.
The following is multiple choice question (with options) to answer.
What type of feeders are earthworms? | [
"middle",
"top",
"deposit",
"oil"
] | C | Earthworms are deposit feeders. They burrow through the ground, eating soil and extracting organic matter from it. Earthworm feces, called worm casts, are very rich in plant nutrients. Earthworm burrows help aerate soil, which is also good for plants. |
SciQ | SciQ-3715 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
What part of the plant is the main site of photosynthesis? | [
"soil",
"stem",
"root",
"leaf"
] | D | 30.4 Leaves Leaves are the main site of photosynthesis. A typical leaf consists of a lamina (the broad part of the leaf, also called the blade) and a petiole (the stalk that attaches the leaf to a stem). The arrangement of leaves on a stem, known as phyllotaxy, enables maximum exposure to sunlight. Each plant species has a characteristic leaf arrangement and form. The pattern of leaf arrangement may be alternate, opposite, or spiral, while leaf form may be simple or compound. Leaf tissue consists of the epidermis, which forms the outermost cell layer, and mesophyll and vascular tissue, which make up the inner portion of the leaf. In some plant species, leaf form is modified to form structures such as tendrils, spines, bud scales, and needles. |
SciQ | SciQ-3716 | inorganic-chemistry
Title: Why is the ratio between Silicon and Oxygen 1:3 in single chain silicates? I thought that the ratio of silicon to oxygen in a silica tetrahedron was 1:4, so if a single chain is just many of these linked together, why does the ratio become 1:3? Silicon has 2 complete oxygen atoms ($2\times1=2$) and 2 equally shared oxygen atoms ($2\times1/2=1$), total 3.
The following is multiple choice question (with options) to answer.
Aluminosilicates are formed by replacing some of the si atoms in silicates by which atoms? | [
"ce",
"ad",
"al",
"fe"
] | C | character increases. Silicates contain anions that consist of only silicon and oxygen. Aluminosilicates are formed by replacing some of the Si atoms in silicates by Al atoms; aluminosilicates with threedimensional framework structures are called zeolites. Nitrides formed by reacting silicon or germanium with nitrogen are strong, hard, and chemically inert. The hydrides become thermodynamically less stable down the group. Moreover, as atomic size increases, multiple bonds between or to the group 14 elements become weaker. Silicones, which contain an Si–O backbone and Si–C bonds, are high-molecular-mass polymers whose properties depend on their compositions. |
SciQ | SciQ-3717 | electric-circuits, electric-fields, electrical-resistance, capacitance, batteries
Initially, the total electric field between the plates of the capacitor is the one produced by the circuit in the ambient space, which was found to be zero. And since there are no forces which cause charge carriers to accumulate on one of the plates, the field between the plates will remain zero.
This state of affairs contradicts circuit theory, which predicts an electric field will form between the plates due to an accumulation of charge carriers on one of the plates.
What is the resolution? Unfortunately, this question straddles the boundaries between circuit theory and electromagnetism. Such questions are rather out of scope for a circuit theory class and disappointingly they are usually not well covered in an electromagnetism course. I will try to bridge both or answer with both theories as much as possible.
At steady state, the charge carriers are circulating around the circuit at constant speed through the conducting wires. From this we can conclude that the battery is doing no work on the charge carriers,
This conclusion is incorrect. From a circuit theory point of view the battery has a non-zero current and voltage and therefore the $P=IV$ is also non-zero (positive). From an electromagnetism point of view the work on charge carriers is given by $\mathbf E \cdot \mathbf J$ which is also positive inside the battery.
The fact that the speed is constant does not imply that the work done by the battery is zero. Similarly, the gears on the pedal of a bicycle do positive work on the chain even though the speed of the chain does not increase. There is simply another source that is doing negative work.
Since the circuit is neutrally charged overall, there is no electric field in the ambient space outside of the circuit.
The only nonzero electric field is contained within the battery and resistor themselves, and their fluctuations are responsible for the net increase in kinetic energy of the particles inside the resistor.
The following is multiple choice question (with options) to answer.
In a smoke detector, a battery in the electric circuit creates what between the metal plates? | [
"magnetism",
"voltage",
"hydrogen",
"cooling"
] | B | Most of us have at least one device in our homes that guards our safety and, at the same time, depends on radioactivity to operate properly. This device is a smoke detector. A typical smoke detector contains an electric circuit that includes two metal plates about 1 cm apart. A battery in the circuit creates a voltage between the plates. Next to the plates is a small disk containing a tiny amount (∼0.0002 g) of the radioactive element americium. The radioactivity of americium ionizes the air between the plates, causing a tiny current to. |
SciQ | SciQ-3718 | meteorology, climate-change, gas, pollution
Title: Regarding various types of atmospheric pollution Does all the car pollution (from about 150 million cars at least in the U.S. and a lot more in all of North America and the rest of the world) all the smoke-stack pollution of various factories and all the Airline pollution running day after day have a deleterious and damaging effect on the general atmosphere and, over time, the climate?
Given all the observed pollution that China has caused itself and some of the resulting weird weather events there this certainly seems to be evidence of the damaging effects of car and factory pollution. Has anyone calculated how much exhaust from cars is produced in one day on average in a 'moderate' sized city?
Of course it seems with all the increased oil production in the U.S. and elsewhere we, human beings are going to keep are love-affair with gas-powered cars for the next 200 or 300 years. That is if we don't use up all the oil and gas in the ground before then. As a USA resident, the EPA is the best place to start when wondering about the emissions inventory of atmospheric pollutants or pollutant precursors that affect the National Ambient Air Quality Standards (e.g. Particulate Matter, Carbon Monoxide, Sulfur Dioxide, Lead, Nitrogen Oxides, Volatile Organic Compounds). The EPA compiles a comprehensive emissions inventory of all criteria pollutants at the county level which is available in the National Emissions Inventory (compiled once every 3 years). You can see the summary of your county at http://www.epa.gov/air/emissions/where.htm. As for the effects of atmospheric pollution, it is important to consider the lifetime of said pollutants in the atmosphere in order to put their environmental impacts into perspective. For instance, the air pollutants covered by the National Ambient Air Quality Standards have immediate health effects when high concentrations are breathed in regularly. Both animals and plants are adversely affected by these irritating and sometimes toxic chemicals, but these pollutants are also reactive and do not last long in the atmosphere unless they are constantly being replenished (e.g. daily traffic). Air quality also impacts critical nitrogen loads on ecosystems and possible production of acid rain.
The following is multiple choice question (with options) to answer.
Photochemical smog consists mainly of what? | [
"acid",
"carbon",
"ozone",
"oxygen"
] | C | Secondary pollutants form from primary pollutants. Many occur as part of photochemical smog . This type of smog is seen as a brown haze in the air. Photochemical smog forms when certain pollutants have a chemical reaction in the presence of sunlight. Photochemical smog consists mainly of ozone (O 3 ). Ozone near the ground is a pollutant ( Figure below ). This ozone is harmful to humans and other living things. However, ozone in the stratosphere protects Earth from the Sun's harmful ultraviolet radiation. |
SciQ | SciQ-3719 | zoology, sensation
Title: Can animals that rely heavily on sonar sense colour? Apparently there're species around as rely heavily on sonar to sense the world around them.
E.g. Bat, Dolphin, Whale ...
The humans, and other terrestrial beings in a lighted world are capable of distinguishing colour in varying degrees of acuity. Is this ability to sense colour in our environment applicable to species (terrestrial, avian, and marine) that rely heavily on sonar? Any animal using sound cannot sense color though sonar directly, though these animals are not entirely blind and can probably see colors in the infrared we can't.
Even on the darkest night there is some light around and all bats use this. Old World fruit bats have colour vision, which is useful to them as they are often quite active in daytime, roosting on trees in exposed positions, rather than tucked away in dark crevices like most microbats, which can see only in black-and-white.
Dolphins have additional senses in addition to seeing they can sense electrical fields. So if an animal has its eyes covered, they will seem to be able to do things you would not expect. Its not the same as seeing the color though.
Such animals using sonar can additionally sense density and hardness as well as other material attributes which would cause the acoustic properties of the material as well as movement.
A hard-bodied insect produces a different quality of echo from one with a soft body, so bats can distinguish between some different groups of insects in this way. They can also determine the size of the object.
What's really interesting is that even human beings can experience this unusual sense. Blind people have learned to echolocate by making clicks with their mouth, and there is a movement to teach this skill.
Anyone can try it. In just an hour or two I was able to tell how close I was to a wall, whether the wall was concrete. I couldn't play video games (2:20 on the link) or see colors though.
The following is multiple choice question (with options) to answer.
What lizards can change colors based on the color of their surroundings? | [
"geckos",
"skink",
"chameleons",
"Monitor"
] | C | |
SciQ | SciQ-3720 | organic-chemistry, inorganic-chemistry
But then, some inorganic compounds do have carbon too, and there may even be some compounds that some call organic, and others call inorganic, like $CO_2$.
As I have felt it, in my learnings so far, it's like inorganic chemistry is the default chemistry and organic chemistry goes a step beyond.
But I don't quite grasp the difference.
What is the real semantics behind the word "organic"?
For example, we humans are made of loads of water, and that's a pretty organic thing to me. But then, water is inorganic.
Diamonds are the carbon top of the cake, and do not transmit the idea of being an "organic" thing.
Another very confusing thing are polymers, chanins of loads of carbons with other elements, in many shapes and textures. To me, a piece of "plastic" is not a very organic thing, but indeed, they are!
That brings the semantics into an even more confusing level.
And of course, there must be historical reasons for those chosen words.
Could someone please point out where this distinction comes from and why it is important?
With all my respect to science and the people who made chemistry a useful thing. This question is not about critics, it's about not knowing the facts, so of course I am the ignorant here.
Related and useful: What is the definition of organic compounds? IUPAC is the International Union of Pure and Applied Chemistry, they make recommendations on the nomenclature. IUPAC mentions that the difference between organic and inorganic is not distinct. To quote "The boundaries between ‘organic’ and ‘inorganic’ compounds are blurred." in Brief Guide to the Nomenclature of Inorganic Chemistry R. M. Hartshorn, K.-H. Hellwich, A. Yerin.
Since the terminology of organic vs. inorganic is all human classification, it is not a binary system 0 or 1. What we can say now is that traditionally, all organic compounds do contain carbon. It can come from natural sources or purely synthetic. There is no such restriction. Plastic is an organic compound because it contains a lot of carbon chains.
Note that this word organic, as used in chemistry, has nothing to with the buzz word used in marketing of organic food, organic fruits, organically grown stuff. The word organic comes from French organique designating the jugular vein, hence related to organs or living beings.
The following is multiple choice question (with options) to answer.
Lipids are organic compounds that consist of carbon, hydrogen, and? | [
"helium",
"methane",
"oxygen",
"nitrogen"
] | C | Lipids are organic compounds that consist of carbon, hydrogen, and oxygen. They are made up of fatty acids and other compounds. They provide cells with energy, store energy, and help form cell membranes. |
SciQ | SciQ-3721 | newtonian-mechanics, forces, reference-frames, acceleration, inertia
Also, I don't know what you mean by force getting "used up".
You need an net non zero force on the object to give it an acceleration. Perhaps I can say that the net force is used up in increasing the objects momentum. (if that can make you understand)
When you hit the ball with a golf club:
The following is multiple choice question (with options) to answer.
What do you call the force a machine applies to an object? | [
"drop force",
"premium force",
"optimal force",
"output force"
] | D | When you use a machine, you apply force to the machine. This force is called the input force. The machine, in turn, applies force to an object. This force is called the output force. The output force may or may not be the same as the input force. The force you apply to the machine is applied over a given distance, called the input distance. The force applied by the machine to the object is also applied over a distance, called the output distance. The output distance may or may not be the same as the input distance. |
SciQ | SciQ-3722 | kinematics, acceleration, rotation
Yes, in fact they're almost completely unrelated.
The average acceleration is defined as
$$\vec a_\text{avg} = \frac{\Delta\vec v}{\Delta t}$$
It is one quantity that partially describes the motion of a particle over an extended time. In other words, average acceleration encapsulates the fact that a particle started with some velocity at time A and ended with some velocity at time B, but completely ignores what the particle did between A and B. This is by design.
Centripetal acceleration, on the other hand, is an instantaneous quantity: it's the radial component of acceleration. (This requires that you have chosen some point to be the center of a polar coordinate system.) It partially describes the motion of a particle at one moment, not over an extended time.
The following is multiple choice question (with options) to answer.
In scientific terms, average acceleration is the rate at which what changes? | [
"gravity",
"volume",
"direction",
"velocity"
] | D | In everyday conversation, to accelerate means to speed up. The accelerator in a car can in fact cause it to speed up. The greater the acceleration, the greater the change in velocity over a given time. The formal definition of acceleration is consistent with these notions, but more inclusive. Average Acceleration Average Acceleration is the rate at which velocity changes,. |
SciQ | SciQ-3723 | inorganic-chemistry
Title: Why do metals tend to lose electrons, as opposed to maintaining electric neutrality? Metals tend to lose electrons to obtain the stable noble gas configuration of 8 valence electrons.
Why do they want to obtain this configuration, and how does the strength of their "desire" to obtain this configuration compare with the "desire" to maintain neutral charge. If the answer depends on the chemical, I'm happy for you to provide some examples.
Thanks. Firstly, atoms "want" to achieve the noble gas configuration of 8 valence electrons because it is the most stable form. All that means is that it doesn't tend to react under normal conditions that we experience on Earth, therefore it will stay in that configuration for quite a while and are less likely to react. There is a more complex quantum physical answer for that but you'll have to go elsewhere for than.
The main force that keeps electrons in atoms is the electrical attraction between the electrons and the protons in the nucleus and so, if it is more energetically favourable to lose that electron in order to form a bond, then that is what will happen.
Focusing on the Alkali metals as an example, as you move down the group, they get more and more reactive. This is because of two main reasons that are a result of the electrons being further away from the nucleus:
Because they're further away, the attraction between the protons and the outer most electron is less
Secondly, taking Rubidium as an example, it has 37 electrons and 37 protons. From the perspective of the outer-most electron, there are 36 electrons repelling it, and 37 protons attracting it, therefore acting as a net charge of 1. However, if you take into account the first point, the repulsion of the closer electrons is stronger than the attraction of the protons so it could even be less than one
The following is multiple choice question (with options) to answer.
Some atoms are more stable when they gain or lose an electron and form what? | [
"molecules",
"ions",
"protons",
"electrons"
] | B | Ions and Ionic Bonds Some atoms are more stable when they gain or lose an electron (or possibly two) and form ions. This fills their outermost electron shell and makes them energetically more stable. Because the number of electrons does not equal the number of protons, each ion has a net charge. Cations are positive ions that are formed by losing electrons. Negative ions are formed by gaining electrons and are called anions. Anions are designated by their elemental name being altered to end in “-ide”: the anion of chlorine is called chloride, and the anion of sulfur is called sulfide, for example. This movement of electrons from one element to another is referred to as electron transfer. As Figure 2.11 illustrates, sodium (Na) only has one electron in its outer electron shell. It takes less energy for sodium to donate that one electron than it does to accept seven more electrons to fill the outer shell. If sodium loses an electron, it now has 11 protons, 11 neutrons, and only 10 electrons, leaving it with an overall charge of +1. It is now referred to as a sodium ion. Chlorine (Cl) in its lowest energy state (called the ground state) has seven electrons in its outer shell. Again, it is more energy-efficient for chlorine to gain one electron than to lose seven. Therefore, it tends to gain an electron to create an ion with 17 protons, 17 neutrons, and 18 electrons, giving it a net negative (–1) charge. It is now referred to as a chloride ion. In this example, sodium will donate its one electron to empty its shell, and chlorine will accept that electron to fill its shell. Both ions now satisfy the octet rule and have complete outermost shells. Because the number of electrons is no longer equal to the number of protons, each is now an ion and has a +1 (sodium cation) or –1 (chloride anion) charge. Note that these transactions can normally only take place simultaneously: in order for a sodium atom to lose an electron, it must be in the presence of a suitable recipient like a chlorine atom. |
SciQ | SciQ-3724 | thermodynamics, energy, earth, thermal-radiation
@Benjohn has given you the correct answer. Here is my take.
The ultimate heat provider of the earth ( except a small percentage of heat from the magma at the center of the earth) is the sun. It pours down at the surface about 1.2 kilowatts of energy per meter square ( which btw is directly used by solar panels). The same energy falls on the surface of the moon whose surface burns up during its daytime and freezes by black body radiation at night.
The earth is fortunate to have a gas atmosphere which mitigates the extremes of the possible temperatures that the ground would reach otherwise. An example of mitigation is what happens at the sea floor. Most of the energy is picked up by the water and the floor is kept at a steady temperature with small changes day and night in the first meters from the surface, depending on the season, radiating away with the black body radiation, but the body of water has such large heat capacity that variations are small.
The gas atmosphere is a more temperamental "blanket", its heat capacity depends on several gases , called green house gases from the bad impression that agricultural green houses work that way ( they do not, they work by inhibiting heat exchange by convection but that is another story, on which there is no controversy).
The main green house gas is water , H2O. It is worth contemplating this figure :
Solar irradiance spectrum above atmosphere and at surface. Extreme UV and X-rays are produced (at left of wavelength range shown) but comprise very small amounts of the Sun's total output power.
We see that H2O has the most absorption spectrum for infrared wavelengths, (which are the wavelengths of heat )and then comes CO2. Green house gases absorb both incoming and reflected from the surface of the earth infrared, and as most of the reflected wavelengths are in the infrared they act as a slowing down of the black body radiation that would finally leave the earth. As a blanket keeps a person warmer green house gases by playing ball with infrared radiation ( the wavelengths where heat is really transferred) keep the surface of the earth into a reasonable temperature for life, lucky us.
The following is multiple choice question (with options) to answer.
Like a blanket on a sleeping person, greenhouse gases act as what for the planet? | [
"Exterior Coverings",
"plastic",
"insulation",
"ventilation"
] | C | Like a blanket on a sleeping person, greenhouse gases act as insulation for the planet. The warming of the atmosphere is because of insulation by greenhouse gases. Greenhouse gases are the component of the atmosphere that moderate Earth’s temperatures. |
SciQ | SciQ-3725 | thermodynamics, atoms, phase-transition
But let's look at how the states change. In a solid, you have a bunch of atoms that can be thought of as masses connected by springs. As heat is added to the system, the atoms begin to vibrate in the lattice of springs. As more heat is added, they vibrate enough to break the springs. This is when the solid begins to melt and turn to a liquid.
Now you have a liquid where the atoms are all moving around but they aren't free to move wherever they want. More heat is added to the system and the atoms begin to translate faster and faster. Eventually they translate fast enough to overcome the forces that are holding them together in a liquid. Now they fly free and are a gas.
So ultimately, heat is energy that makes atoms and molecules move in some way. They may translate, rotate, vibrate, or the electrons may begin moving around depending on how much heat is there and what configuration the molecule has.
The following is multiple choice question (with options) to answer.
What is the process in which a solid changes directly to a gas without going through the liquid state called? | [
"vaporization",
"sublimation",
"amplification",
"Diffusion"
] | B | Sublimation is the process in which a solid changes directly to a gas without going through the liquid state. Solid carbon dioxide is an example of a substance that undergoes sublimation. |
SciQ | SciQ-3726 | newtonian-mechanics, forces, mass, acceleration
And is "the body accelerating" thus by (4) ?
(4) $= {N \textbf{F} \over M}$ is the reason for the title "Force on body = multiple ?"
Considering objects on earth are known to be made of "few" "things" occupying volume (but not assuming the number of kind of particle in (3) is 1) $N$ might be the same value for every object. Thus "is earths gravity determined too big by a factor of billions?". Alright, so the situation here as you have presented focuses on how the earth pulls upon one particle whose mass is the total mass divided by number of particles represented as M/N, and the force as F. And then you said because the acceleration is the same for the small particle, it should also apply for the object at large because the object is not expanding or shrinking in anyway. And so far, the reasoning is on the right track but has some issues.
The issue with this is the force changing because you are dealing with an individual particle instead of the whole mass. The calculation you have shown says the gravitational force applied to the entire mass with its entire magnitude, also applies to each individual particle with its entire magnitude. This is where the issue comes from because the force actually decreases because equation for gravity is net F=Fg=mg. So actually for the equation you derived, Fg would be M/N times g because that is the force on each individual particle. Then if you solve for acceleration, you get M/N times g divided by M/N for mass and you a=g which is as you would expect if the object was in free fall.
So all in all we just derived above that the individual accelerations are actually g down so now we can extrapolate that since individual accelerations are g down, it means the entire acceleration of the object is g down because the object isn't changing shape or size.
So no, Earth's gravity is not too big; it perfectly matches the correct gravitational acceleration
The following is multiple choice question (with options) to answer.
How many forces do objects on earth have acting on them at all times? | [
"three",
"ten",
"two",
"four"
] | C | More than one force may act on an object at the same time. In fact, just about all objects on Earth have at least two forces acting on them at all times. One force is gravity, which pulls objects down toward the center of Earth. The other force is an upward force that may be provided by the ground or other surface. |
SciQ | SciQ-3727 | human-biology, reproduction, human-genetics
Title: Very frequent multiple births in humans 18th century Feodor Vassilyev is said to have had children by two wives, each of whom only ever had twins, triplets or quadruplets. His first wife has 16 sets of twins, 7 of triplets and 4 of quads; his second had 6 sets of twins and 2 of triplets. Is there any known plausible biological explanation for this, or do we have to dismiss it as a fabrication?
I could understand a woman's body being unusually susceptible to multiple births. I can't find information on whether these women tended to have monozygotic or polyzygotic offspring, but neither option seems unviable to me. However, since it's unlikely two of Feodor's sexual partners would share such a trait, one would think to attribute it to him. Presumably there would have to be a mechanism by which paternal DNA can trigger embryo fissions, in which case I imagine the offspring would be polyzygotic. Risk factors for dizygotic twinning are related to multiple follicular development, and include maternal family history, ethnicity, geography, maternal parity, maternal age, and, of course, use of assisted reproductive technology. There may be a genetic component to monozygotic twinning as well, but that rate is fairly consistent across populations. Other risk factors, such as diet and supplementation, have been proposed, but the data are less robust. There are some interesting studies demonstrating geographic clusters of twinning, but these tend to be demographic clusters that are associated with other risk factors.
Though a higher risk of twinning can be transmitted from a father to his daughters, the father's family history of twinning is not a significant risk factor (for his own children to be twins). To clarify -- if a man has a family history of multiple births, his children are no more likely to be twins than the general population, but his daughers are more likely to give birth to twins. This study is one example of the studies that have shown a significant independent association between maternal family history and twinning, with no significant independent association with paternal family history.
The following is multiple choice question (with options) to answer.
How often does sperm develop in humans? | [
"sporadically",
"monthly",
"continuously",
"rarely"
] | C | |
SciQ | SciQ-3728 | mars, water
Title: What are the most recent minerals modified by water found to date on Mars? There likely was quite a bit of liquid water on the surface of Mars less than 4 billion years ago. We know this because we found rocks that old that have been modified by the presence of water. For example :
If the martian blueberries, or hematite spherules found by Opportunity formed by slow evaporation in mineral-rich liquid water, they likely formed 3 billion years ago.
Serpentines have been detected by CRISM.
What is the most recent rock we know of on Mars that was modified by the presence of liquid water on the surface? If you have access, I would recommend you to read Carter et al. (2013). It is a compilation of all occurrences of hydrous minerals that have been detected on Mars by spectrometers OMEGA (Mars Express/ESA) and CRISM (Mars Reconnaissance Orbiter/NASA). This data was used to investigate the spatial distribution, composition, and age of hydrous minerals on Mars.
Regarding age, the most recent hydrous minerals are opal and zeolites of Amazonian age (< 3 Ga):
The exposure with the youngest unit age is a series of small cones and
dykes or fractures which have been identified thanks to a dust‐free
window in the Utopia Rupes region, in a unit of Amazonian age. Both
opaline silica and zeolites (or alternatively sulfates) are found
there as shown in Figure 7. Zeolites are found mainly on the butte
that could constitute a small volcano, as suggested by the presence of
radial patterns resembling lava flows, to the southeast especially.
Silica is found on an elongated structure which is either a dyke or a
structural horst. Of interest is the presence of two small cones
exposed in the NE corner displaying opaline silica. Such small cones
on Mars have been interpreted either as volcanic vents or mud
volcanoes [e.g., Allen, 1979; Farrand et al., 2005]. In both cases,
the observation of opaline silica pleads for a local fluid circulation
inside a hydrothermal context consistent with volcano‐ice interactions
as predicted by previous studies [Allen, 1979; McGill, 2002; Farrand
et al., 2005].
The following is multiple choice question (with options) to answer.
Scientists found that the youngest rocks on the seafloor were where? | [
"trenches.",
"mid - ocean glaciers",
"mid - ocean sediments",
"mid-ocean ridges"
] | D | The scientists used geologic dating techniques on seafloor rocks. They found that the youngest rocks on the seafloor were at the mid-ocean ridges. The rocks get older with distance from the ridge crest. The scientists were surprised to find that the oldest seafloor is less than 180 million years old. This may seem old, but the oldest continental crust is around 4 billion years old. |
SciQ | SciQ-3729 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
The reproductive tissues of male and female humans develop similarly in utero until a low level of the hormone testosterone is released from male what? | [
"bladder",
"kidneys",
"liver",
"gonads"
] | D | Human Reproductive Anatomy The reproductive tissues of male and female humans develop similarly in utero until a low level of the hormone testosterone is released from male gonads. Testosterone causes the undeveloped tissues to differentiate into male sexual organs. When testosterone is absent, the tissues develop into female sexual tissues. Primitive gonads become testes or ovaries. Tissues that. |
SciQ | SciQ-3730 | evolution, neuroscience
This paper's abstract says all I was saying about the development of neurons and synapses relying on pre-existing molecules and structures:
https://pubmed.ncbi.nlm.nih.gov/2830635/
"Evolution of Neurotransmitter Receptor Systems"
What I'm looking for to find how close science is to answering your question (or if it already has) is papers looking at the phylogenetic relationships of different neurotransmitters and related molecules. That might say a lot about which ones have been used as neurotransmitters the longest. I haven't found this yet but I'll try more tomorrow when I'm not on mobile.
ETA: will re-edit this comment later, but this paper answers your question I believe, or as well as any could at present at least:
https://cichlid.biosci.utexas.edu/sites/default/files/evoneuro/files/liebeskind_et_al_2017.pdf?m=1511200627
"Evolution of Animal Neural Systems"
This paper, which is available in full and is a review paper from 2017, looks at the evolution of every aspect of animal neural systems (i.e. nervous systems mediated by neurons, a concept the paper also defines because the line is apparently blurry). One interesting aspect of it is that while you point to Cnidarians as the most "primitive" nervous systems, the paper points out the latest evidence suggests Ctenophores are the earliest branch off the animal tree, meaning nervous systems either evolved convergently, or sponges lost their nervous systems secondarily, in which case Cnidarians would lose this special status.
The paper has a section about neurotransmitters, which says the following:
The following is multiple choice question (with options) to answer.
Flatworms have a concentration of nerve tissue in the head end, which was a major step in the evolution of what organ? | [
"kidney",
"liver",
"heart",
"brain"
] | D | Flatworms have a concentration of nerve tissue in the head end. This was a major step in the evolution of a brain. It was also needed for bilateral symmetry. |
SciQ | SciQ-3731 | gravity, energy, mass, mass-energy
Title: How does energy convert to matter? To my understanding, matter and energy are one and the same. Shifting from $E$ to $M$ in Einstein's famous equation requires only a large negative acceleration. If $M$ really is $E/c^2$, does that make matter the solid state of energy? I've read a lot about positron-electron collisions at high energies creating larger particles, and there is obvious matter conversion in fusion and fission reactions, but I can't find anything describing the physics of the conversion from energy to matter, rather than the interactions of what is already matter.
Specifically, the thing I'm getting hung up on is the reason energy would take on a solid state in the first place. If energy is represented by waves, how does it become particles? If gravity is determined by mass, and mass is nothing more than static energy, does that make gravity a static-electromagnetic force? Energy and matter are not the same. Matter is a type of thing, whereas energy is a property of a thing, like velocity or volume. So your premise is flawed. In particular:
there's no such thing as "a solid state of energy" - hopefully it makes sense that a property of something does not have states
energy is not represented by waves, though it is a property of a wave. It's also a property of a particle (which, in quantum field theory, is really just a tightly bunched wave).
Note that mass can be converted to energy, because mass actually is energy. It is one of various types of energy: kinetic energy, potential energy, mass energy, and so on. Different types of energy get converted into each other all the time.
I'd suggest looking at several of the questions under the "Related" heading at the right for more information about this. (I actually thought this had been asked here before, but I didn't find an exact duplicate.)
The following is multiple choice question (with options) to answer.
What type of energy travels through matter in wave form? | [
"vibrational",
"light",
"magnetic",
"sound"
] | D | Sound is a form of energy that travels in waves through matter. The ability to sense sound energy and perceive sound is called hearing . The organ that we use to sense sound energy is the ear. Almost all the structures in the ear are needed for this purpose. Together, they gather sound waves, amplify the waves, and change their kinetic energy to electrical signals. The electrical signals travel to the brain, which interprets them as the sounds we hear. |
SciQ | SciQ-3732 | molecular-biology, cell-biology
This rate decreases dramatically as radius of the cell increases. For example a cell with double the diameter (2 micrometers) has a volume eight times larger, so collisions between any two molecules take 8 times ($2^3$) as long to occur (in other words, it takes molecules 8 times longer to "find" each other). This is one reason why there is a kind of upper limit on the size of an individual cell. Bigger organisms are bigger because they have more cells, not because they have larger cells.
The field of biology concerned with how likely it is for a reaction to occur is called enzyme kinetics. A related field, which deals with how frequently molecules collide is called statistical mechanics.
The following is multiple choice question (with options) to answer.
What speeds up chemical reactions inside cells? | [
"catalysts",
"nucleus",
"inhibitors",
"electrodes"
] | A | Living things depend on catalysts to speed up many chemical reactions inside their cells. Catalysts in living things are called enzymes. Enzymes may be extremely effective. A reaction that takes a split second to occur with an enzyme might take billions of years without it!. |
SciQ | SciQ-3733 | physiology, ichthyology
Salmon use to deal with the NaCl fluxes driven by the gradients between the salmon and its surroundings. In their gill epithelial cells, salmon have a special enzyme that hydrolyzes ATP and uses the released energy to actively transport both Na+ and Cl- against their concentration gradients. In the ocean, these Na+-Cl- ATPase molecules 'pump' Na+ and Cl- out of the salmon's blood into the salt water flowing over the gills, thereby causing NaCl to be lost to the water and offsetting the continuous influx of NaCl. In fresh water, these same Na+-Cl- ATPase molecules 'pump' Na+ and Cl- out of the water flowing over the gills and into the salmon's blood, thereby offsetting the continuous diffusion-driven loss of NaCl that the salmon is subject to in fresh water habitats with their vanishingly low NaCl concentrations.
Reference
Reference
The following is multiple choice question (with options) to answer.
What atmosphere do gills help exchange gas in? | [
"air",
"stratosphere",
"ecosystem",
"water"
] | D | |
SciQ | SciQ-3734 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
Community interactions are important factors in what? | [
"natural process",
"natural selection",
"natural change",
"natural resources"
] | B | A community is the biotic component of an ecosystem. It consists of the populations of all the species that live in the same area. Populations in communities often interact with each other. Community interactions are important factors in natural selection. They help shape the evolution of the interacting species. Types of community interactions include predation, competition, and symbiosis. You’ll read about each type of interaction in this lesson. |
SciQ | SciQ-3735 | botany, terminology, fruit
Title: What is the name of this part in plants, fruits, vegetables? What is the name of this part of the plant, fruit, vegetable? The thing that the plant is connected with the tree and gets nutrients with? The part we usually cut out when eat fruit.
Examples below
Papaya
Banana
Mango 'Stalk' or 'pedicel' would be an appropriate term (see, for example, this paper or this one). Specifically, you could say 'terminal part of the stalk/pedicel', though I don't know if there is a word for that.
Note that the term pedicel is commonly used for the stalk of a flower; it makes sense to use it for fruits too as they are derived from flowers.
The following is multiple choice question (with options) to answer.
The end of a pine tree branch bears the male cones that produce what? | [
"the ovaries",
"oxygen",
"the pollen",
"the stigmas"
] | C | John Haslam. The end of a pine tree branch bears the male cones that produce the pollen . CC BY 2.0. |
SciQ | SciQ-3736 | geophysics, seismology, instrumentation
Title: How can I calculate the sensitivity of a seismometer? I would like to know if a specific seismometer can measure 1 micron/sec velocity. I have a few specs from the datasheet but I'm not a seismologist and am trying to figure out how to relate the specs to one another.
I have:
Velocity output band: 30s (0.03Hz) to 100 Hz
Output Sensitivity: 2400 V/m/s
Peak/Full scale output: Differential: +- 20V
Sensor dynamic range: 137 dB @ 5 Hz
Thanks in advance! This is a partial answer because I'm not an expert and because I don't know what the dynamic range of 137 dB means. Hopefully you can add a little more information.
tl;dr: if 137 dB is the dynamic range in power, then it's 68.5 dB in voltage and velocity which sounds more plausible, and makes the velocity sensitivity well below 1 micron per second. However we don't yet know what the noise and bandwidth of your signal are yet so we can't evaluate that.
I have a few specs from the datasheet...
The more information you share from the data sheet the better although I've now just noticed that the question is about three years old.
Also, there may be some helpful insight at How sensitive are typical seismometers?
The following is multiple choice question (with options) to answer.
One seismogram indicates the distance to the what? | [
"researchers",
"houses",
"epicenter",
"the moon"
] | C | One seismogram indicates the distance to the epicenter. This is determined by the P-and S-wave arrival times. If a quake is near the seismograph, the S-waves arrive shortly after the P-waves. If a quake is far from the seismograph, the P-waves arrive long before the S-waves. The longer the time is between the P-and S-wave arrivals, the further away the earthquake was from the seismograph. First, seismologists calculate the arrival time difference. Then they know the distance to the epicenter from that seismograph. |
SciQ | SciQ-3737 | python, beginner
Title: Generating complementary DNA sequence I am still relatively new to Python but I have been actively doing sample examples to try and get used to problem solving aspect of programming.
With that said, I stumbled upon a question that asks you to write a code to convert DNA strand to its complementary form.
What I have written works, but I don't believe that my approach is efficient enough. Could you please review my code and guide me as to how I might improve on it? I feel like there will be a faster way than writing multiple if, elif statements.
import sys
def check_input(user_input):
if len(user_input) == 0:
sys.exit("No strand provided.")
return user_input
def complementary(strand):
complementary_strand = ''
for dna in strand:
if dna == 'A':
complementary_strand += 'T'
elif dna == 'a':
complementary_strand += 't'
elif dna == 'T':
complementary_strand += 'A'
elif dna == 't':
complementary_strand += 'a'
elif dna == 'G':
complementary_strand += 'C'
elif dna == 'g':
complementary_strand += 'c'
elif dna == 'C':
complementary_strand += 'G'
elif dna == 'c':
complementary_strand += 'g'
else:
complementary_strand += 'x'
return complementary_strand
if __name__ == "__main__":
user_input = input("Enter strand: ")
print()
strand = check_input(user_input)
complementary_strand = complementary(strand)
print("Complementary strand is {}".format(complementary_strand)) Typically, a character-for-character replacement is best done using str.translate():
strand.translate(str.maketrans('AaTtGgCc', 'TtAaCcGg'))
However, your situation is trickier, because you also want to map all invalid characters to 'x'. To achieve that, you would need to read the str.maketrans() documentation carefully, and figure out that you can wrap the mapping in a collections.defaultdict.
from collections import defaultdict
The following is multiple choice question (with options) to answer.
What is the process of creating complementary strands of mrna called? | [
"differentiation",
"division",
"transcription",
"mutation"
] | C | Overview of Transcription. Transcription uses the sequence of bases in a strand of DNA to make a complementary strand of mRNA. Triplets are groups of three successive nucleotide bases in DNA. Codons are complementary groups of bases in mRNA. Every triplet, or codon, encodes for a unique amino acid. |
SciQ | SciQ-3738 | geology, mineralogy
There is an adage amongst some geologists that states "gold is where you find it". There is no altitude preferable for finding gold deposits. It's found in mountains, in deserts, in forests, under salt lakes, even dissolved in the oceans. The oceans contain the largest quantities of gold, but it is uneconomic to extract it from sea water because the concentration are so low.
Biological indicators, such a vegetation may work for some base metals, such as copper, but not necessarily for gold.
Also, gold can occur as a deposit of just gold, but it can also occur in association with other metals in the form of polymetallic deposits which contain gold, silver, copper, lead or zinc, even uranium.
Finally, not all deposits of minerals, gold included, are reserves. To be classified as a reserve and an orebody, a deposit of mineralization must be economic to mine.
The following is multiple choice question (with options) to answer.
In ancient egypt gold mines were the property of what? | [
"prospectors",
"state",
"city",
"people"
] | B | But mining for gold is a slow, dirty, and dangerous process. Not everyone owns a gold mine – in both the ancient Egyptian society and during the Roman Empire, the gold mines were the property of the state, not an individual or group. So there were few ways for most people to legally get any gold for themselves. |
SciQ | SciQ-3739 | zoology, marine-biology
Title: Why do stranded marine mammals die so quickly? Mammals have lungs, so do marine mammals. Nevertheless some marine mammals seem to die rather quickly when they strand on a beach.
As they have lungs and can breath while on land, why do they die so quickly? Not being in water only restricts them from food.
Do they maybe try to get back into the water so rudely that they get hurt by rocks and/or break bones? Pressure difference doesn't seem to be a problem as they can jump out of the water as well.
I was wondering after reading this article on stranded pilot whales that got spot but died rather quickly after. In the case of whales, I always thought that it was something to do with the fact that they rely upon buoyancy to support their weight and this seems to support that view:
When whales, including small whales or dolphins become stranded on beaches
they suffer from the pressure of their own weight on their organs,in the
water they are weightless. They also suffer from overheating as they have
blubber that insulates them in the water and outside of the water causing
them to overheat. This is why we place wet towels and cold water on their
fins and flukes when do they strand to help keep their body temperature
down. Unfortunately most stranded whales do not survive once they have
beached themselves.
The following is multiple choice question (with options) to answer.
The arid environment of a desert, for instance, can quickly deplete an animal of what? | [
"protein",
"strength",
"air",
"water"
] | D | |
SciQ | SciQ-3740 | organic-chemistry, terminology
Title: Why carbon is so special? One special branch in chemistry is allotted to compounds of only one element (carbon). Is it justified when there are more than 115 elements and their compounds but not with any special branches? Carbon has a valency of four which helps in bonding with other atom or groups easier and adds to catenation. When one talks of Carbon's ability to bond, then Catenation property should come to your mind. Catenation is the linkage of atoms of the same element into longer chains. Catenation occurs most readily in carbon, which forms covalent bonds with other carbon atoms to form longer chains and structures. This is the reason for the presence of the vast number of organic compounds in nature. One such marvel is DNA! So, while studying chemistry, Carbon compounds form a class of peculiar natured compounds and the vast range of molecules and development of their own domain in their own scale might have made people feel that a separate category should be made for Carbon compounds because of their vastness and availability, also predominately manifestation of them in almost every thing, even life! In fact life became possible only because of Carbon, such is the importance. They have got their own nomenclature system in their domain.. Its really vast. The study of everything begins with Organic compounds first.. be it isomerism, medicinal reaction or anything. So, you may see, how important Carbon is. If you are a biology student, you must have learned about biomolecules.. DNA and gene pool, replication, transcription, translation, protein coding, defective proteins and some viral components and its lifecycle. Molecular basis of genetics is based on DNA and other organic compounds. That gives you thrilling experience to see how stuffs work and wonder about their importance and manifestation. Carbon is a wonder.
The following is multiple choice question (with options) to answer.
What type of chemistry is the study of chemicals containing carbon called? | [
"biochemistry",
"inorganic chemistry",
"bioanalytical chemistry",
"organic chemistry"
] | D | Organic chemistry is the study of chemicals containing carbon. Carbon is one of the most abundant elements on Earth and is capable of forming a tremendously vast number of chemicals (over twenty million so far). Most of the chemicals found in all living organisms are based on carbon. |
SciQ | SciQ-3741 | hematology, red-blood-cell
So, menstrual "blood" is a combination of sloughed off stromal and glandular tissue, broken down vascular cells and blood, and, no, it is not highly oxygenated (it's kind of darker than normal blood. It doesn't carry any "decoded DNA". It's basically a waste product at this point, dead, dying and no longer functional tissue.
Virgin's flow is just as dead as non-virgin's flow. Cultures obtained at hysterectomy indicate that the endometrial cavity is normally sterile. The major difference between a virgin and a non-virgin is that the possibility of infection of endometrial tissue exists in non-virgins.
Of course myths will arise around menstrual flow. After all, when it was alive, it was the medium for implantation of a blastocyst. But they are just myths.
Endometrium Histology
Infections as a Cause of Infertility
The following is multiple choice question (with options) to answer.
What is the muscular organ shaped like an upside-down pear that has a thick lining of tissues called the endometrium? | [
"uterus",
"lungs",
"kidney",
"liver"
] | A | The uterus is a muscular organ shaped like an upside-down pear. It has a thick lining of tissues called the endometrium . The lower, narrower end of the uterus is known as the cervix . The uterus is where a fetus grows and develops until birth. During pregnancy, the uterus can expand greatly to make room for the baby as it grows. During birth, contractions of the muscular walls of the uterus push the baby through the cervix and out of the body. |
SciQ | SciQ-3742 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
What includes all the biotic and abiotic factors in an area and how they interact? | [
"habitat",
"biome",
"ecosystem",
"tundra"
] | C | An ecosystem is a unit of nature. It consists of all the biotic and abiotic factors in an area and all the ways in which they interact. |
SciQ | SciQ-3743 | thermodynamics, electromagnetic-radiation, infrared-radiation, solar-cells
Title: Is IR radiative cooling of solar cells a valid efficiency improvement? I am interested in photonics and I stumbled across the following article:
E. Rephaeli, A. Raman, and S. Fan, "Ultrabroadband Photonic Structures To Achieve High-Performance Daytime Radiative Cooling", Nano Lett. 2013, 13, 4, 1457–1461.
But is IR radiative cooling really viable? If there's some water in the air, it closes the "atmospheric window" that makes the outer space a cold heat sink. Also I see that this way of cooling is mainly researched by a small group of related researchers who reciprocally cite their articles.
So is it a really interesting option or just a kind of scientific hobby? I think such a technology has real application in space solar cells where heat management is real issue because it can only be managed via radiation.
Maybe other applications include terrestrial concentrator photovoltaics. In these solar cells optics are used to concentrate sunlight up to around 1000x, so heat management again becomes important. However, probably easier to do with a heat sink.
That said, conduction of heat is proportional to $\Delta T$ where as radiative cooling (in the blackbody limit - and these are not black emitters) is $\Delta T^4$. Also the heat sink temperature is on the order of 300K where as space is 2.7K! So intrinsically the temperature gradient is larger.
I can see potential for cost reductions too. That is, replacing any heat sink technology with a 2 micrometre layer incorporated into the growth process of the solar cell is attractive!
As for the point about it being niche and the circular references. Sometimes this is how things start. Someone has an idea, there is a flurry of activity and it dies away or it is picked up and ran with by everyone. I wouldn’t judge the quality of the science in that metric.
The following is multiple choice question (with options) to answer.
What is used for cooling detectors of infrared telescopes? | [
"liquid nitrogen",
"carbon dioxide",
"hand nitrogen",
"material nitrogen"
] | A | Detecting Electromagnetic Waves from Space A final note on star gazing. The entire electromagnetic spectrum is used by researchers for investigating stars, space, and time. As noted earlier, Penzias and Wilson detected microwaves to identify the background radiation originating from the Big Bang. Radio telescopes such as the Arecibo Radio Telescope in Puerto Rico and Parkes Observatory in Australia were designed to detect radio waves. Infrared telescopes need to have their detectors cooled by liquid nitrogen to be able to gather useful signals. Since infrared radiation is predominantly from thermal agitation, if the detectors were not cooled, the vibrations of the molecules in the antenna would be stronger than the signal being collected. The most famous of these infrared sensitive telescopes is the James Clerk Maxwell Telescope in Hawaii. The earliest telescopes, developed in the seventeenth century, were optical telescopes, collecting visible light. Telescopes in the ultraviolet, X-ray, and γ -ray regions are placed outside the atmosphere on satellites orbiting the Earth. The Hubble Space Telescope (launched in 1990) gathers ultraviolet radiation as well as visible light. In the X-ray region, there is the Chandra X-ray Observatory (launched in 1999), and in the γ -ray region, there is the new Fermi Gamma-ray Space Telescope (launched in 2008—taking the place of the Compton Gamma Ray Observatory, 1991–2000. PhET Explorations: Color Vision Make a whole rainbow by mixing red, green, and blue light. Change the wavelength of a monochromatic beam or filter white light. View the light as a solid beam, or see the individual photons. |
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